Objective:To observe the clinical efficacy of Wentong Powder with Shenque acpoint application in the treatment of primary dysmenorrhea with syndrome of blood stasis due to coagulated cold, and discuss its possible mechanisms. Methods72 patients of primary dysmenorrhea with syndrome of blood stasis due to coagulated cold were randomly divided into the treatment group and control group, 36 cases in each group. The control group was treated with ibuprofen sustained release capsules and the treatment group was treated with acpoint application of Wentong Powder at Shenque point (CV8),with a course of 2 menstrual cycles. The Chinese medical syndrome score was compared, and the changes on the serum levels of cyclooxygenase-2 (COX-2), prostaglandin F,2,α (PGF,2,α), prostaglandin E,2, (PGE,2,), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), estradiol (E,2,) and progesterone (P) were observed and compared.  Results:①In both groups, there was statistically significant difference on Chinese medical syndrome score between treatment before and after (P,<,0.05). After treatment, the improvement on Chinese syndrome score in the treatment group was obviously better than that in the control group (P,<,0.05). ②Compared with treatment before, the levels of COX-2, PGF2α and PGF,2,α/PGE2 were significantly decreased in both groups after treatment (P,<,0.01), the level of PGE2 was significantly increased in the treatment group (P,<,0.01) but obviously decreased in the control group (P,<,0.01). After treatment, there were statistically significant differences on the levels of COX-2, PGF2α and PGE,2, between the two groups (P,<,0.01), while there was no statistically significant difference on the level of PGF,2,α/PGE,2, between the two groups (P＞0.05). ③Compared with treatment before, the levels of IL-6 and TNF-α were significantly decreased in both groups after treatment (P,<,0.01). After treatment, there were statistically significant differences on the levels of IL-6 and TNF-α between the two groups, and the levels in the treatment group were obviously lower than those in the control group (P,<,0.05). Compared with treatment before, the E,2, level was significantly increased in the treatment group (P,<,0.01) but no obvious change was found in the control group (P,>,0.05) after treatment. There was no obvious change on the P level in both groups (P,>,0.05). After treatment, the E,2, level in the treatment group was significantly higher than that in the control group (P,<,0.01). ④During the trial, no adverse reactions were observed in both groups, and no abnormality in routine examinations of blood, urine, stool and liver and kidney function was detected in both groups before and after treatment.  Conclusion:Wentong Powder with Shenque acpoint application in the treatment of primary dysmenorrhea with syndrome of blood stasis due to coagulated cold can significantly improve the dysmenorrhea in patients. Its mechanisms may be related to increasing E,2, decreasing COX-2, IL-6 and TNF-α and regulating PGs (decreasing PGF,2,α and increasing PGE,2,).