OBJECTIVE： To establish a method for the simultaneous determination of paeoniflorin， cinnamaldehyde， psoralen and isopsoralen in Yaotong capsules. METHODS：HPLC method was adopted. The determination was performed on Agilent-C18 column with mobile phase consisted of acetonitrile-water （gradient elution） at the flow rate of 1.0 mL/min. The detection wavelengths were set at 240 nm （paeoniflorin， psoralen， isopsoralen） and 290 nm （cinnamaldehyde）. The column temperature was 35 ℃， and sample size was 10 μL. RESULTS： The linear ranges of paeoniflorin，cinnamaldehyde，psoralen and isopsoralen were 0.004 02- 0.100 6 mg/mL（r＝0.999 8）， 0.024 50-0.612 7 mg/mL（r＝0.999 8），0.005 24-0.131 0 mg/mL（r＝0.999 9），0.005 11-0.127 8 mg/mL（r＝0.999 9）， respectively. LOQ were 37.17， 1.47， 21.76， 25.57 ng， respectively； LOD were 11.15， 0.44， 6.53， 7.67 ng， respectively. RSDs of precision， stability and reproducibility tests were all lower than 2.0％. The recoveries were 99.02％-100.83％（RSD＝0.68％，n＝6）， 98.58％-100.99％（RSD＝0.83％，n＝6），99.78％-101.69％（RSD＝0.89％，n＝6）， 100.06％-102.46％（RSD＝0.92％，n＝6）， respectively. CONCLUSIONS： The method is simple， accurate and suitable for simultaneous determination of  paeoniflorin， cinnamaldehyde， psoralen and isopsoralen in Yaotong capsules.