To observe the clinical efficacy of the treatment for acute attack of knee osteoarthritis(KOA) from damp heat and stasis toxics syndrome. Methods:A total of 90 cases of patients with KOA were randomly divided into two groups equally. The control group were treated with Meloxicam Dispersible Tablets, while the treatment group with modified SimiaoYongAn Decoction. The overall efficacy and the changes of the WOMAC scores were compared between the two groups after the treatment. Results: The total effective rate of the treatment group was 88.89%, while the control group was 86.67%. The total effective rate had no significant differences between the two groups (P＞0.05). The WOMAC scores of the two groups were decreased significantly compared with those before (P<0.01). However, the decline of the treatment group was better than the control group (P<0.05). Conclusion: The total effective rate of modified SimiaoYongAn Decoction was similar with Meloxicam Dispersible Tablets, but the modified SimiaoYongAn Decoction had more advantages in improving knee function and there were fewer side effects. This effective method is worth of further promotion and application.