Based on the self-dependent climate system model, the global-regional double coupling model system for Southern Power Grid region is developed, and the ensemble hindcast experiments from 1991 to 2020 are conducted. The bias correction method suitable for the rainfall prediction of China Southern Power Grid region is developed and a seasonal rainfall prediction system suitable for the Southern Power Grid region has been established. The results show that the global-regional double coupling technique can improve the modelling and prediction capability of the regional rainfall spatial distribution and dominant modes of summer rainfall in the Southern Power Grid region, and the bias correction scheme can significantly improve the prediction skills of summer rainfall anomalies in the region. The 30-year average pattern correlation coefficient can reach 0.27, with prediction score (PS) skill reaching 74.31, and the regional average temporal correlation coefficient is about 0.28. The system also shows good prediction skills for extreme flood and drought years. In general, the system can generate reliable seasonal rainfall forecast products, and hence provide good technology support for the safe operation and deployment management in China Southern Power Grid.