Coilia ectenes is an abundant species in Qingcaosha reservoir and plays an important ecosystem role. Seasonal surveys were conducted in 2011 to sample the specimens of Coilia ectenes for studying their biological property. Statistical approaches were used in data analysis to describe the biological characteristics of Coilia ectenesin Qingcaosha reservoir. The dominant total length (TL) of the samples of both females and males was 20-25 cm with the means of 25 cm and 23.4 cm, respectively. And also, the dominant round weight of different sex samples was same with the range of 20-40 g. The relationships between TL and BW (body weight), TL and DW (dressed weight) of all samples could be described as W_B = 0.0008L_T^3.3983 andW_D= 0.0006L_T^3.4286. Pearson correlation analysis showed a positive correlation existing in both gonad weight versus total length and gonad weight versus round weight for different sex samples. Moreover, it showed a trend that the gonad weight of Coilia ectenes increased with both their total length and round weight. The sex ratio of the samples of C.ectenes was 2.6∶1 which was not in accord with 1∶1. The gonad analysis indicated that more mature individuals were found in May and July, and the dominant maturity samples were mainly at stageⅡwhich accounted for 69.6% for femals and 72.2% for males; Furthermore, the mature individuals ’gonad somatic index (GSI) was obviously higher than immature individuals’ and the immature individuals’ GSI tended to increase with total length and conversely for the mature individuals’. The main prey of Coilia ectenes was shrimp and the feeding intensity was mostly in the class 0 and 1 which accounted for 61.11% of the total in the samples.