OBJECTIVE：To establish the method for content determination of 6 active ingredients in Paeonia lactiflora during different harvest periods ，and to investigate its variation rules so as to determine the optimal harvesting period. METHODS ：HPLC method was adopted to determine the contents of gallic acid ， catechin， alibiflorin， paeoniflorin， benzoic acid and benzoylpaeoniflorin，and principal component analysis was conducted . The determination was performed on Thermo C 18 column with mobile phase consisted of acetonitrile- 0.1％ phosphoric acid aqueous solution （gradient elution ）at the flow rate of 1.0 mL/min. The detection wavelength was 230 nm，and column temperature was 35 ℃. The sample size was 10 µL. RESULTS ：The linear range of the above 6 ingredients were 0.013 2-0.25 mg/mL（r＝0.999 2），0.013 2-0.25 mg/mL（r＝0.999 9），0.026 8-0.51 mg/mL（r＝0.999 7）， 0.42-8.01 mg/mL（r＝0.999 2），0.016-0.31 mg/mL（r＝0.999 4），0.02-0.38 mg/mL（r＝0.999 8），respectively. The limits of quantification were 0.009 3，0.008 5，0.016 3，0.021 7，0.011 3，0.017 4 mg/mL，and the limits of detection were 0.003 3，0.002 7， 0.005 4，0.007 3，0.003 8，0.005 9 mg/mL. RSDs of precision ，stability and repeatability tests were less than 2％. The recoveries were 96.01％-99.43％（RSD＝1.23％，n＝9），97.95％-100.45％（RSD＝0.79％，n＝9），97.98％-100.11％（RSD＝0.68％，n＝ 9），98.83％ -100.09％ （RSD＝0.65％ ，n＝9），98.58％ - 100.95％（RSD＝1.35％，n＝9），96.28％-103.26％（RSD＝ 1.76％，n＝9）. The contents of above 6 ingredients in Radix Paeoniae Rubra （roots） were 0.016％ -0.057％ ，0-0.067％ ， 0.207％-0.640％，2.350％-5.887％，0.030％- 0.245％，0.054％- 0.381％，respectively. On May 30th，the drying rate of Radix 0451-87266873。E-mail：wangzhen_yue@163.com Paeoniae Rubra was the lowest （about 33％），and on Sept. 15th，the drying rate was the highest （about 49％）. The contents of gallic acid and paeoniflorin in the leaves of P. lactiflora were higher than the root during Jul.-Oct. Results of principal component analysis showed that the variance contribution rates of the first two principal components were 71.845％ and 18.170％，respectively；cumulative variance contribution rate was 90.015％. The months with higher comprehensive scores were May to Jun. and Sept. to Oct. CONCLUSIONS ：Established method is simple ， accurate，reproducible and precise. It can be used to determine the contents of 6 active ingredients in Radix Paeoniae Rubra during different harvest periods. Sept. 30th to Oct. 15th is the optimum harvesting periods for Radix Paeoniae Rubra ，and leaves can be harvested around Jul. 15th.