OBJECTIVE： To investigate the rationality of TLC identification method （3） of （R，S）-epigoitrin in Isatis indigotica stated in 2015 edition of Chinese Pharmacopeia （partⅠ） （later abbreviated as pharmacopeia）， and make some improvements. METHODS： Three batches I. indigotica were collected and prepared into decoction pieces according to the processing method of I. indigotica in pharmacopoeia. TLC identification of （R，S）-goitrin in I. indigotica decoction piece and medicinal material were conducted according to identification method （3） in pharmacopeia （80％ ethanol as solvent for sample treatment， ultrasound extraction）； the rationality of pharmacopoeia method was investigated. Then the method was improved by changing the extraction solvent and pretreatment method （method one： using water as solvent， ultrasound extraction； method two： soaking in water for 1 h， then adding into methanol， ultrasound extraction； method three： the sample was wetted and then dried， using 80％ methanol as solvent， ultrasound extraction） of samples， and the optimal method was verified. According to the optimal method， the TLC identification of （R，S）-goitrin was detected by using chromatographic plates from different manufacturers， under the conditions of low temperature and low humidity （7 ℃， relative humidity 48％） and high temperature and high humidity （35 ℃， relative humidity 75％） respectively，to investigate the durability of the method. RESULTS： According to the method of pharmacopeia， in the chromatograms of decoction pieces， the same color spots appeared at the corresponding chromatographic positions of reference substance， but no corresponding spots appeared in the medicinal material chromatograms. After the samples were treated by three improvement methods， in medicinal material chromatograms， the same color spots appeared in the corresponding chromatographic positions of reference substances. There were single chromatographic spot after medicinal materials were treated with method one， and there were more spots after medicinal materials were treated with method two and three， and method two consumed less time than method three. The results of validation tests and method durability tests  showed that after the treatment of I. indigotica and its decoction pieces according to method two， the same color spots appeared in the corresponding positions of the decoction pieces and the medicinal materials chromatograms as those of the control. CONCLUSIONS： The improved TLC identification method is effective， the chromatographic spots are clear， and the repeatability is good.