Abstract: An intert ropical convergence zone (ITCZ) synt hesis index is designed,which can demonst rate quite clearly and objectively the seasonal features of deep convection in ITCZ regions.ITCZ activities are analyzed by means of the index for both wet and dry summers of North China.The results show that the differences between wet and dry summers are more remarkable in winter-spring period,especially in Indian and East Asian monsoon regions,which could be able to provide a new method to the prediction of summer rain in North China.