Based on summer precipitation data from North China and MJO Index, NCEP/NCAR reanalysis circulation data, the paper uses a variety of statistical methods to analyze the relationship between MJO and summer precipitation in North China and its influence mechanism. The results show that: Summer, MJO has a good relationship with summer precipitation in North China. When MJO enters the 5th and 6th phases, there will be a clear precipitation process in summer in North China. In terms of the influence mechanism, MJO induced the occurrence of favorable water vapor transport anomaly in the summer of North China through the propagation of high and low disturbances to medium and high latitudes, resulting in the occurrence of heavy precipitation in North China during the summer. Specifically, in terms of water vapor conditions, MJO can enhance the transmission of south wind vapor (corresponding to RMM1) or southeast wind vapor(corresponding to RMM2) in North China by affecting the 850 hPa wind field, thus contributing to the occurrence of summer precipitation in North China; In terms of dynamic rising conditions, MJO has contributed to the summer precipitation process in North China by affecting the deepening of the 500 hPa Baikal trough and the strengthening of the subtropical high near the Korean peninsula, as well as the enhancement of the tropospheric upward movement over North China. MJO can be used to make extended period prediction of summer precipitation in North China.