Objective: Observing human to mouse one-way mixed lymphocyte culture(xMLC) and the effect of new immunosuppressant-Rapamycin on XMLC. Methods: Mouse splenic lymphocyte were collected and treated by mitomycin as activating cell; Human Peripheral blood lymphocytes(hPBL)were separated and gathered as reacting cell; Mouse splenic lymphocyte and hPBL wee mixed to incubate for 1 week; The researchers designed control、RPM groups,and experiment(drugs)grup have different concentration. Results: HPBL in the experiment groups (mixed mouse lymphocyte)proliferated obviously,the amount of3H-TdR in corporation increased evidently(P<0 05,The mean percentage of CD 4, CD 8, LgG, LgM positive cells rose markedly. HPBL in the experiment groups less proliferated,the amount of 3H-TdR incorporation declined,RPM's ic50(50%inhibition concentration)approximately in 1.5 nmol/L; the mean percentage of CD 4, CD 8, IgG, IgM positive cells fell obviously. Conclusion: The human to mouse one-way MLC has obvious lymphocyte proliferation. New immunosuppressants-Rapamycin have powerful effete on XMLC.