To investigate the clinical characteristics and related factors of dysmenorrhea in patients with endometriosis(EM).Methods:This case-control study was conducted on 2 056 patients with EM from 42 hospitals in China from January 2019 to December 2021.A questionnaire survey was used to collect and sort out the medical records of the selected subjects.According to whether they had dysmenorrhea or not，patients were divided into the dysmenorrhea group(n=1 097) and non-dysmenorrhea group(n=959).Univariate and multivariate logistic regression analysis methods were used to compare the clinical characteristics between the two groups and analyze the clinical characteristics of dysmenorrhea in patients with EM and the related factors affecting the occurrence of dysmenorrhea.Results:1) The incidence of dysmenorrhea in patients with EM was 53.4%.The incidence of five accompanying symptoms，including fear of cold，dizziness，poor appetite，anal distension，and sexual intercourse pain in the dysmenorrhea group was higher than that in the non-dysmenorrhea group，and the difference was statistically significant(P<0.05). 2) The results of the univariate analysis showed that there were significant differences between the two groups in age，as well as whether they had EM surgery，western medicine treatment，sexual life，and adenomyosis(P<0.05). 3) Multivariate logistic regression analysis showed that EM dysmenorrhea was correlated with age，EM surgery，and sexual life(P<0.05).Conclusion:Dysmenorrhea is a common symptom in patients with EM.Patients with EM dysmenorrhea often show accompanying symptoms such as fear of cold，dizziness，poor appetite，anal distension，and sexual intercourse pain.Age≤25 years old is the risk factor of EM dysmenorrhea; age>35，EM surgery，and sexual life are the protective factors of EM dysmenorrhea.Clinical practice should comprehensively consider the above related factors for early diagnosis and treatment，which will help to reduce and eliminate the focus and alleviate the pain of patients.