Objective  Method for determination of acyclovir in plasma was developed.Method  The plasma level of acyclovir was determined by high performance liquid chromatography.Result  The sample was extracted by separation on C    18   column with amobile phase of mixture of methanol∶acetic acid(99∶1).The UV detector wavelength was set at 254?nm.The sensitivity of detection afforded by acyclovir was found to be 0.022?mg·L    -1  .The standard curve was a linear in 0.022～4.40?mg·L    -1   range. The average recovery was>90% and the variations of inter  day and intra  day were less than 10% and 13%,respectively.Conclusion  The method is simple,sensitive,accurate and has been applied to pharmacokinetic studies in human.