Recently, the relationship between the Madden-Julian Oscillation (MJO) and the El Niño-Southern Oscillation (ENSO), the numerical simulation (forecasting) of the MJO, and the influences of the MJO on weather and climate have become some of the major issues at the forefront of atmospheric science. Studies of the interaction between the MJO and ENSO and their results has been reviewed in previous papers; therefore, in this paper we present a comprehensive overview of recent research advances by Chinese scientists on the MJO’s influence on weather and climate, as well as numerical simulation (forecasting) of the MJO. The studies used the Australian Bureau of Meteorology Real-time Multivariate (RMM) MJO index to investigate the relationship between MJO and typhoon activity over the northwest Pacific. The results show that the MJO plays a significant role in modulating the genesis of the typhoon over the northwest Pacific. For the typhoon genesis number over the northwest Pacific, the ratio between the active and inactive periods of the MJO is 2:1. During the MJO active period, the ratio of the northwest Pacific typhoon genesis number between phases 2-3 of the MJO in which the convection center of the MJO is located in the tropical eastern Indian Ocean and MJO phases 5-6 where the convection center of the MJO is located in the western Pacific is also 2:1. Composite atmospheric circulations show that the distribution of the dynamic typhoon-influencing factors and heating sources of the western Pacific in the different MJO phases are very different. In phases 2-3 of the MJO, all the factors tend to suppress the development of convection and typhoons in the western Pacific. In MJO phases 5-6, however, these factors promote convection development and create a favorable large-scale background circulation for the generation and development of typhoons. The composites of the 30-60 day low-frequency kinetic energy at the 850 hPa level for the typhoon-rich years show positive low-frequency kinetic energy anomalies over the northwestern Pacific east of the Philippines and south of 15°N, indicating that the MJO activity is strong in that region. In contrast, on typhoon-poor years, negative low-frequency kinetic energy anomalies are found over the monsoon trough regions of the northwestern Pacific east of the Philippines suggesting that the MJO activity is weaker over that region. Generally speaking, there are more (less) typhoons over the northwestern Pacific in the years when the MJO activity over the northwestern tropical Pacific is strong (weak). Corresponding to the different MJO phases, the precipitation over eastern China is anomalous whether in winter or spring. In spring, during MJO phases 2-3, the middle and lower reaches of the Yangtze River are wetter, while South China is drier. During MJO phases 4-5, South China is wetter while the middle and lower reaches of the Yangtze River are drier. During the other phases of the MJO, the anomalous precipitation of eastern China is negative. In winter, during phases 1-3 (especially phases 2-3), South China is wetter; during phases 6-8 (especially phases 6-7) South China is drier. In summer, the MJO over the Indian Ocean (the western Pacific) can influence southeastern China through the wave-train effect of the westerly jet in the lower troposphere (the meridional circulation and subtropical high over the western Pacific) which results in a wetter (drier) season in southeastern China. Moreover, the continual anomaly of the MJO over the tropical middle-east Indian Ocean has a clear impact on summer rainfall in Yunnan on an interannual time-scale. The atmospheric circulation analysis and numerical simulations all show that strong convection for the different phases of the MJO will generate different teleconnection patterns (Rossby wave train). These will result in favorable (or unfavorable) circulation and conditions for rainfall in different regions of China, which is the primary mechanism responsible for the precipitation anomalies associated with the MJO. The simulation (prediction) of the MJO in the numerical model is far from success and still an open question. Our series of numerical simulations clearly indicates that the simulation of the MJO strongly depends on a convective parameterized scheme in the model; whether the model can reproduce a realistic diabatic heating profile of the tropical atmosphere is the key to a successful simulation of the MJO. The MJO activities in the model match those of the observations to a certain degree only when the maximum of the heating profile is located in the middle and lower troposphere. The results of these simulations are consistent with our previous theoretical studies.