Glyceraldehyde-3-phosphatede hydrogenase(GAPDH)is one of the basic enzymes that maintain the life activities.In this paper,gapdh gene was isolated from the mud crab,Scylla paramamosain using RT-PCR and RACE methods.The obtained full-length cDNA of GAPDH was 1 440 bp with an open reading frame of 1 008 bp encoding a putative peptide of 335 amino acids.By alignment,the amino acid sequence of S.paramamosain GAPDH showed high homology with those of some other animals.It suggested gapdh was highly conservative.Real-time PCR showed that the gapdh gene was expressed in various tissues,and highly expressed in thoracic ganglia,eyestalk ganglia,ovary and epidermis.During the ovarian development,the expression of gapdh mRNA was significantly higher at early-developing stage(Ⅱstage)and lowest at ripe stage(Ⅴstage).It indicated that GAPDH might play an important role in cell mitosis in ovary of the mud crab.