Objective: Observing human to mouse one-way mixed lymphocyte culture(xMIC) and the effect of new immunosuppressant-Rapamycin on XMIC. 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 of3 H-TdR in corporation increased evidently( P ＜ 0.05, The mean percentage of CD4, CD8, 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 CD4, CD8, 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.