Objective: The main purpose of this paper was to prepare the immunoactive peptides from Meretrix meretrix Linnaeus (MLIP) by enzymatic hydrolysis， optimize the enzymolysis conditions of MLIP， and studied its immune activity. Method: MLIP was used as raw material， and five commonly used proteases were chosen to hydrolyze. The proliferation rate of RAW264.7 cells was selected as an indicator to screen the most suitable protease for enzymolysis solution. Then， the single factor test was carried out， and three factors with significant impact were selected to optimize the enzymolysis conditions by response surface method， and MLIP was prepared with the optimized process parameters. In addition， this research also studied the effects of different concentrations of MLIP on the relative proliferation rate， cell morphology and NO release of RAW264.7 cells. Results: The proliferation rate results showed that complex protease was the most suitable enzyme to prepare MLIP. The optimal enzymatic parameters obtained by response surface optimization were: pH 6.8， solid-liquid ratio 1∶6.2， enzyme dosage 3 493 U/g， enzymolysis at 45 ℃ for 3 hours. The relative proliferation rate of RAW264.7 cells was predicted to be 71.40%， which were basically the same with the results obtained by verification experiment. In addition， RAW264.7 cells showed the best proliferation promoting effect when the concentration of MLIP was 0.4 mg/mL. All dose of MLIP caused differentiation to varying degrees of cell differentiation and had a certain promoting effect on the release of NO of RAW264.7 cells. Conclusion: The results indicated that the MLIP exhibit desirable immune activity， which might provide reference for the preparation and further study of the MLIP.