Based on the fishery data collected by bottom trawls during the spawning season (May, 2007 and May to June, 2008) in coastal waters of the East China Sea, the relative stock density and distribution of hairtail Trichiurus lepturus and the biological characteristics and reproductive characteristics of its spawning stock were studied. The results showed that the relative stock density of hairtail spawning stock were 13.07±5.17 kg/h, 14.34±6.64 kg/h, and 16.10±6.28 kg/h in May, 2007, May and June, 2008, respectively, and accounted for 63.55%, 60.20% and 53.77% of the total catch, respectively. The occurrence frequencies of the fish were more than 85% in three surveys. The average anal length of hairtail spawning stock was 182.62 mm, and the dominant anal length was 150～200 mm; Average body weight was 102.77 g, and the dominant body weight ranged from 50 g to 110 g. There was no significant difference in body weight and anal length relationship between spawning males and females (P>0.05), and the body weight and anal length relationship was W= 4.520×10-5 L2.795 (R2=0.929, n=349). According to Chi-square test, there were significantly more females than males in the spawning stock, and the group with the anal length less than 210 mm was dominant. Anal length at 50% sexual maturity (L50) of female and male were 164.65 mm and 171.65 mm, respectively.