Under global warming, North China is frequently affected by heat waves. It is crucial to improve the seasonal prediction of hot extreme in North China. Land-atmosphere interaction plays an important role in the formation of summer heat waves in North China. The memory ability of soil moisture provides a potential forecasting factor for seasonal prediction of heat waves in North China. In this paper, based on statistical analysis and multiple sensitivity tests using the WRF (Weather Research and Forecasting Model) model, we find that the relationship between preceding soil moisture anomalies and summer heat waves in North China is influenced by the strength of the West Pacific subtropical high (WPSH). When the WPSH is strong, the southerly winds on its west side carry a large amount of water vapor from the tropics to the southern parts of North China and increase the precipitation in the region, which is not conducive to the maintenance of the preceding soil moisture dry anomaly, thus limiting the contribution of the preceding soil moisture anomaly to the heat waves. On the contrary, when the WPSH is weak, the soil moisture dry anomalies in North China can last for a longer time and lead to heat waves. The intensity of the WPSH is related to the sea surface temperature (SST) in the tropical central-eastern Pacific. When the tropical Pacific SST anomaly is in the warm phase in summer, the WPSH is relatively weak and the precipitation in North China is low, which is conducive to the maintenance of dry soil conditions in North China. Under such circumstances, the preceding soil moisture anomaly can be used as the prediction signal of heat wave in North China.