The lipid accumulations during the stages of the ovarian fast maturation( from September to December) and their ef fect on the spawning of Eriocheir sinensis were studied. The results shown that gonadosomic index ( GSI ) and lipid content were significantly increased, both neutral lipids ( PL ) ( mainly triacylglycerol and cholesterol) and phospholipid( PL) ( mainly phosphatidylethanmine) were responsible for the increase in ovarian lipid, and NL increasing from 1 3. 67% to 20. 12% ovary dry weight , PL f rom 7 . 21% to 10. 70% ovary dry weight . The ratio of NL/ TL or of PL/ TL remained relatively constant during the fast ovarian development , and NL concentration of ovary were always higher than that of PL. The fatty acid composition of lipids, PL and NL of ovaries varied markedly during this development stage. There was much more long-chain polyunsaturated fatty acids such as C20B5 and C22B6in the mature ovary than those at the start of fast development of immature ovary ( NL P < 0. 05; PL P < 0. 01) , but the percentage of C20B4 decreased signif icantly ( P< 0. 01) during this stage. It was also found the mature crab that could not spawn was partly because of their lower PL content( %ovarian dry wt ) and lower percentage of the C20B5 and C22B6 in PL than that of normal mature ovaries in Dec. The results suggest that the lipid, manily phospholipid and long-chain polyunsaturated fatty acids such as C20B5and C22B6 are essential for ovarian fast development and must be obtained from dietary source.