The invention relates to an active decapeptide of Sinonovacula constricta. According to the active decapeptide of Sinonovacula constricta, the amino acid sequence is Ile-Asp-Gly-His-Ala-Ala-Gly-Asp-Val-Gly, and shown by ESI/MS detection, the molecular weight is 835.7Da. The active decapeptide of Sinonovacula constricta is prepared through the following steps: shelling fresh Sinonovacula constricta to take flesh, washing the Sinonovacula constricta flesh, then, smashing the washed Sinonovacula constricta flesh, carrying out tissue homogenizing, and then, adjusting the pH value of the homogenate for later use; and adding pepsase into the homogenate for enzymolysis, carrying out ultrafiltration, G-25gel separation and out-phase high performance liquid chromatography purification on the obtained enzymolysis sample, collecting an elution peak component, and carrying out amino acid sequencing, thereby obtaining the active decapeptide of Sinonovacula constricta. According to the active decapeptide of Sinonovacula constricta, the maximum proliferation inhibition rate to human prostatic carcinoma PC-3 cells can reach over 90%, a theoretical basis can be provided for research on prostatic carcinoma resisting drugs, and the active decapeptide of Sinonovacula constricta has great significance in further researching developing drugs and food based on the active decapeptide of Sinonovacula constricta and increasing the economic value of the active decapeptide of Sinonovacula constricta.