Sanjie Analgesic Capsule was approved by CFDA in 2004, produced by means of modern technology by Jiangsu Kanion Pharmaceutical Co., Ltd. The study is a multi-center, double -blind, placebo-controlled, randomized in Chinese subjects with endometriosis-associated pain to assess treatment effect and safety in the subjects treated with Sanjie Analgesic Capsule versus subjects treated with placebo.