Objective To compare the sensitivities of the stimulation effect of human cord blood mesenchymal stem cells(CB-MSCs) and CB-MSCs of neuronal differentiation to lymphocytes(LCs) detected with carboxyfluorescein didcetate(CFSE) and MTT. Methods To prepare LCs from SD rat and divided into four group stimulating cells: 1. CB-MSCs; 2. Dif-CB-HSCs; 3. SH-SY5Y（positive control）; 4. Auto-LC（negative control）.Stimulating cells were respectively Co-cultured with LCs. The proliferation of LCs was detected with MTT and CFSE (EM>n/EM>=3). Results CB-MSCs and Dif-CB-HSCs stimulated LCs to proliferate more weakly than positive control detected with MTT and CFSE. The quantity of proliferation of lymphocytes Co-cultured with CB-MSCs and Dif-CB-HSCs were higher than that of Auto-LC detected with CFSE. But MTT OD value of CB-MSCs and Dif-CB-HSCs was a little lower than that of Auto-LC. Statistical analysis results showed no significant difference.Conclusion CFSE can reflect proliferation status of lymphocytes better than MTT. CFSE shows mor