Objective To observe the effect of extracorporeal shock wave therapy with different energy flux density on the short-term effect of the patients with knee osteoarthritis in the early and middle stage. Methods 150 knee joints with osteoarthritis were divided into five groups: A, B, C, D and E. The energy flux density of each group was 0.06 mJ/mm2, 0.10 mJ/mm2, 0.14 mJ/mm2, 0.18 mJ/mm2, 0.22 mJ/mm2, respectively. Limb pain visual analogue score(VAS score), Lysholm score and WOMAC osteoarthritis index score was used to evaluate the clinical effect in before treatment, 1 month and 12 months after treatment. Results At 1 month and 12 months after treatment, VAS scores and WOMAC scores were significantly lower than those before treatment (P<0.05), Lysholm scores were significantly higher than those before treatment (P<0.05); At the same time, VAS and WOMAC scores of D group were significantly lower than others (P<0.05), Lysholm scores of D group was significantly higher than others (P<0.05). Conclusion ESWT with medium and low energy flux density can effectively relieve pain symptoms and improve joint function in the patients with knee osteoarthritis in the early and middle stage. Besides, the short-term clinical effect is better when the energy flux density is 0.18 mJ/mm2.