To determine the content of isopsoralen in Gushuling Capsule. High performance liquid chromatography was performed on C 18 column. The chromatographic conditions were as follows: methanol-water (48∶52) as mobile phase, flow rate being 1.1?mL/min and the detecting wavelength at 245?nm. A good linearity of isopsoralen was shown in the range of 0.0342~0.2736??g, r=0.9998. The average recovery is 92.11%, RSD=1.89% (n=5). The method is with good reproducibility,RSD=2.05%.[Conclusion]This method can supply evidence for the quality control of Gushuling Capsule.