The amino acid composition and molecular weight distribution of oyster whole powder and oyster peptide were analyzed. The effects of different concentrations of oyster powder and oyster peptide on the synthesis and secretion of testosterone， dihydrotestosterone and cyclic guanosine monophosphate（cGMP） in mouse leydig cells （TM3 cells） were studied to provide a basis for improving the sexual function of oyster peptides. The effects of oyster whole powder and oyster peptide on the survival rate of TM3 cells were determined by MTT colorimetric assay. The contents of testosterone， dihydrotestosterone and cGMP were detected by enzyme-linked immunosorbent assay. Nitrate reductase method was used to determine the content of nitric oxide （NO） and the activity of SOD in the cells was detected by nitroblue tetrazolium （NBT） chromogenic assay. The results showed that the oyster whole powder and oyster peptide had rich amino acid composition， the oyster peptide contained more essential amino acids and arginine， and the oyster peptide had a molecular weight of less than 1 000u as high as 92.1264%. Compared with oyster whole powder， oyster peptide could significantly promote the secretion of testosterone， dihydrotestosterone and cGMP in TM3 cells， significantly enhance the synthesis of NO in TM3 cells， and increase the SOD activity of TM3 cells， indicating that oyster peptides had promoting functions. The role of its mechanism may be related to the improvement of the NO-cGMP pathway by oyster peptides.