We cloned full length cDNA of ELOVL6 gene(GenBank accession KT779219) in Eriocheir sinensis using genetic homology and RACE methods.The full sequence was 2247 bp, including of 235, 873 and 1139 bp of 5'-URT, ORF and 3'-URT. ELOVL6 gene specified a protein of 290 amino acids which got all of ELOVL features: six transmembrane-spanning regions, one diagnostic histidine box HXXHH motif, several conservative regions and ER retention signal KXKXX.The phylogenetic tree estabilshed by the Neighbor Joining method showed that ELOVL2 is clustered closely with ELOVL5 and ELOVL6 is clustered by itself. At the same time, ELOVL6 of Chinese mitten crab is the closest to the ELOVL6 of Litopenaeus vannamei. Its biochemical function characterized by heterologous expression showed that it caused reduction of C16:0 and C16:1n-7 and increase of C18:0 and C18:1n-9, while produced new product C18:1n-7. Relative gene expression levels of ELOVL6 mRNA in nine tissues and three kinds of different lipids formula feed by quantitative real-time PCR.The results suggested that ELOVL gene was expressed in all of these tissues and it was highest in the hepatopancreas, while lower in the cranial ganglia and thoracic ganglia, and trace in the other tissues. Real-time Q-PCR also revealed that on one side, levels were expressed in hepatopancreas, ovary, transcripts and muscle, on the other side, levels were highest in the hepatopancreas when fed the SO diet compared with the FO diet and FO/SO diet.The results above showed that E. sinensis ELOVL6 could catalyze the production of C16 long-chain fatty acids including both saturated and monounsaturated fatty acids which laid a base for PUFA biosynthesis and its function was influenced by different levels of lipids. Thus, it provided a foundation for fatty acids biosynthetic pathway and its regulation mechanism.