An online solid phase extraction-high performance liquid chromatographic(Online SPE-HPLC) method was developed for the determination of mycophenolic acid in human plasma.Plasma samples were directly injected into the online SPE-HPLC system after simple protein precipitation.Capcell PAK MF Ph-1 was employed as an online SPE column and Poroshell 120 EC-C18 was employed as an analysis column.Results showed that there was a good linear relationship for mycophenolic acid in the concentration range of 020-5000 μg/mL,with a correlation coefficient(r) of 0999 8.The limit of detection(LOD) and limit of quantitation(LOQ) were of 007 μg/mL and 020 μg/mL,respectively.The spiked recoveries for mycophenolic acid in human plasma at three spiked levels of 039,2500 and 5000 μg/mL ranged from 962% to 105%,with intra assay relative standard deviations(intra RSD) of 26%-31% and inter assay relative standard deriation(inter RSD) of 29%-33%.The method was rapid and simple,and was suitable for the determination of mycophenolic acid concentrations in human plasma.