Objective：To explore the value of premenopausal risk of ovarian malignancy algorithm（ROMA） based upon preopearative CA125 and HE4 in distinguishing ovarian endometriosis（OEM） from epithelial ovarian cancer（EOC）. Methods：Between August 2013 and September 2015，293 premenopausal patients with pelvic mass admitted and undergone surgery in our hospital were collected. Two to five days before the surgery，the level of preoperative serum CA125 and HE4 was measured by electrochemiluminescence immunoassay. The ROMA index of premenopausal pelvic mass was calculated using ROMA software. Results：（1）Premenopausal OEM patients were significantly younger with the medium age of 32 than those in EOC group with the medium age of 45（P=0.000），similar to EOB group（40 years old）（P=0.252）.（2）The levels of premenopausal CA125，HE4，ROMA index was higher in EOC group than those in EOB and OEM groups（P=0.000），whereas no significant difference was found in the level of HE4 and ROMA index between EOB and OEM groups（HE4：P=0.482，ROMA：P=0.992）. （3）Early EOC usually hold similar CA125 level to OEM group（P=0.808），with diagnostic sensitivity of 77.42％and specificity of 20.13%，respectively. And the sensitivity，specificity，positive predictive value，negative predictive value for diagnosing EOC were 51.61%，97.32%，80.00%，90.63%for HE4 and 67.74%，84.56%，47.73%，92.63% for premenopausal ROMA（cutoff value was 7.4%） index，respectively. In contrast，when the optimal cut-off value of preme-nopausal ROMA index was 11.65 based on the Youden index through ROC curve，the specificity and positive predictive value could be optimized to 93.96% and 70.00% for early stage EOC. Conclusion：Although it needs further testifying，the cutoff value of preme－nopausal ROMA of 11.65% might be helpful to differentiate ovarian endometriosis from epithelial ovarian cancer.