Abstract: In this paper, the actual yields data of summer maize of 96 counties in Henan province from 1971 to 2010 were used to analyze the risk of yield loss of summer maize. The risk assessment indices included the mean yield reduction rate, variance coefficient of yield reduction rate, risk probability and risk index of yieldreduction of summer maize, and a comprehensive risk assessment indicator was established based on these indices. The risk regionalization of yield loss of summer maize in Henan province was completed. The results showed that the geographic distribution of these risk indicators value had evident regional and continuous characteristics. According to the comprehensive risk index, summer maize planting region in Henan province was divided into three risk categories of high, medium and low. The low risk area including the plain areas of northern and eastern Henan, middle parts of Henan and Nanyang basin; the medium risk area including western hilly area and southern rain fed summer maize area, and the high risk area including Xincai, Shangcai, Pingyu, Shenqiu and Mianchi counties which had the highest yield reduction risk and weaker anti disaster ability. The results of this research could provide a reference for summer maize production and disaster prevention and mitigation in Henan province.

Key words: Summer maize, Yield reduction, Risk assessment, Regionalization