Abstract：Objective：To observe the curative effect of the therapy of Huoxue Dingtong Prescription on knee osteoarthritis(KOA) of blood stasis due to qi stagnation type in early and middle stage. Methods： A total of 120 patients with KOA of blood stasis due to qi stagnation type were selected and divided into the treatment group and the control group according to the random number table methos， with 60 cases in each group. The control group was treated with intra- articular injection with sodium hyaluronate assisting Celecoxib Capsules， and the control group was additionally treated with Huoxue Dingtong Prescription based on the treatment of the control group. The clinical effects and scores of Visual Analogue Scale(VAS)， Lysholm scores of knee joints and levels of pain mediators，including prostaglandin E2(PGE2)，substance P (SP)，proinflammatory factors，including interleukin-1β(IL-1β) and matrix metalloproteinase-3(MMP-3)， and anti- inflammatory factors ， including transforming growth factor- β1(TGF- β1) and interleukin- 13 (IL- 13)， in the two groups before and after treatment were observed and compared. Results： The total clinical effective rate was 95.00% in the treatment group and 83.33% in the control group，the difference being significant(P＜0.05). Before treatment， there was no significant difference being found in the comparisons of scores of VAS and Lysholm scores for knee joints between the two groups(P＞0.05)；after treatment， the scores of VAS in the two groups were decreased when compared with those before treatment(P＜0.05)， and the Lysholm scores for knee joints were increased(P＜0.05)， and the improvement in the above two scores in the treatment group was better than that in the control group(P＜ 0.05). Before treatment， there was no significant difference being found in the comparisons of levels of PGE2 and SP， between the two groups(P＞0.05)； after treatment， the levels of serum pain mediators， including PGE2 and SP，in the two groups were decreased when compared with those before treatment(P＜ 0.05)，and the levels of PGE2 and SP in the treatment group were lower than those in the control group(P＜ 0.05). Before treatment， there was no significant difference being found in the comparisons of levels of proinflammatory factors，including IL-1β and MMP-3，between the two groups(P＞0.05)；after treatment， the levels of IL- 1β and MMP- 3 in the two groups were decreased when compared with those before treatment(P＜0.05)，and the above two levels in the treatment group were lower than those in the control group(P＜0.05). Before treatment， there was no significant difference being found in the comparisons of levels of anti-inflammatory factors，including TGF-β1 and IL-13，between the two groups(P＞0.05)；after treatment，the levels of TGF-β1 and IL-13 in the two groups were decreased when compared with those before treatment(P＜0.05)，and the above two levels in the treatment group were lower than those in the control group(P＜0.05). Conclusion： The therapy of Huoxue Dingtong Prescription combined with routine western medicine can effectively alleviate the pain of patients with KOA of blood stasis due to qi stagnation type in early and middle stage，enhance the knee joint function，and reduce the inflammatory responses.