Abstract: Objective To establish the platform of homogeneous phase enzyme immunoassay for measuring mycophenolic acid（MPA） level in blood and evaluate its stability. Methods Precision and linearity of homogeneous phase enzyme immunoassay and recovery rate of MPA were evaluated,and correlation between MPA and tacrolimus（FK506） levels in blood of patients were analyzed. Results The within-run and between-run coefficient of variation（CV） of MPA were 7.08%,1.49%,2.16% and 8.51%,5.93%,3.12%,respectively,in blood of patients,with a good linearity when MPA was used at the concentration of 0.1-15μg/ml.However,no correlation was found between FK506 and MPA levels in blood when they were used in combination. Conclusion Homogeneous phase enzyme immunoassay is a simple,accurate and stable method for monitoring the MPA level in blood of patients in clinical practice.