In order to measure lymphocyte proliferate responses of murine thymocytes and splenocytes to ConA and LPS, MTT assay was established by optima conditions of culture time, cell concentration and amount of MTT added in experiments. MTT assay has advantages of safety, accuracy, and reliability in comparison with 3H-TdR incorporation assay, the former can be an alternate method of later one. The results of this study demonstrated that there was a significant difference of lymphocyte proliferate responses between murine strains.