In order to study the reproduction of brass gudgeon (Coreius heterodon) in the upper Yangtze River before and after impoundment of the first phase of the Jinsha River Hydroelectric Project(including Xiangjiaba and Xiluodu Dam),the surveys of fish resources of early life stages were carried out in Jiangjin section from May 5 to July 10,2011-2014.Sampling was conducted continuously by conical net.The results showed that C.heterodon accounted for 14.76% of the total 8 014 eggs,the annual average fecundity of C.heterodon was 22.45×10⁷ind.From 2011 to 2014 average daily density of C.heterodon eggs were 8.41,10.57,1.32 and 3.18 ind./1 000 m³ respectively,the average daily density of 2013 and 2014 had significant difference with 2011 and 2012.The correlation between density of C.heterodon eggs and its influence factors found that C.heterodon spawning had significant negative correlation with the transparency,and the transparency of 2013 and 2014 was significantly higher than transparency of 2011 and 2012.According to egg developmental stage and flow velocity,it was inferred that Baisha to Yangshi and Rongshan to Zhaoya section were the main spawning grounds,which were contributing about 56.96% of the total C.heterodon eggs.It indicated that the Jinsha River Hydroelectric Project brought certain impacts to C.heterodon spawning in the upper reaches of Yangtze River,the operation of the first phase of the Jinsha River Hydroelectric Project should consider the environmental requirement of C.heterodon spawning,and a complete fishing ban in spawning grounds should be implernented.