[Aim] To establish a real-time PCR detection method for the genetically modified (GM) Roundup Ready cotton event MON88701, which has not been authorized by the Ministry of Agriculture of China.[Method] The specific primer pairs and probe based on the MON88701 event-specific sequence were designed and then the real-time PCR detection system was established. The specificity, sensitivity and repeatability were analyzed.[Result] The real-time PCR method was specific for detecting MON88701. The limit of quantification (LOQ) was 34 copies MON88701 genomic DNA. Repeatability of the established event-specific real-time PCR method was assessed and the relative standard deviation (RSD) was within the acceptable range.[Conclusion] The established event-specific quantitative real-time PCR method of MON88701 in this study has a good specificity and high sensitivity, and is suitable for the detection of the unathorised event MON88701.