Abstract: Objective To explore the protein overexpression of 5-methyltetrahydrofolate-homocysteine methyltransferase reductase（MTRR）and its clinical significance in ovarian carcinomas. Methods Western blot analysis was used to detect the expression levels of MTRR in 80 ovarian carcinomas,50 benign ovarian tumors and 30 normal ovarian tissues and its association with clinical pathology and multi-drug resistance of ovarian carcinomas was analyzed. Results (1)The expression levels of MTRR increased orderly in normal ovarian tissues,benign ovarian tumors and ovarian carcinomas,and the difference was statistically significant(P<0.05).(2) For ovarian carcinomas,the expression levels of MTRR in clinical stage Ⅰ-Ⅱ and well-differentiated were lower than that in stage Ⅲ-Ⅳ and poor-differentiated.The differences were both statistically significant (P<0.05).(3)The MTRR expression levels in patients with the platinum-resistant were more than that in the platinum-sensitive (P<0.05).After chemotherapy the MTRR levels of progressive ovarian carcinomas were higher than those in remission（P<0.01）.（4）The MTRR expression levels in the mucinous type were lower than that in the serous type(P<0.05).The MTRR levels of ovarian carcinomas with distant organs metastasis were higher than those without metastasis.However,the MTRR levels had no significant association with amounts of ascites and omentum metastasis (P> 0.05).（5）Youden index of ROC curve was 0.681 and the MTRR protein expression was not obvious correlation with median survival time (P>0.05).Cox multivariate analysis also showed that the MTRR protein expression level was not an independent prognostic factor. Conclusion The MTRR protein overexpression were association with generation and progress of ovarian carcinomas;as well as the MTRR protein overexpression could be a potential new biomarker for evaluating of ovarian tumor nature and ovarian carcinomas platinum-multi-drug resistance.