Objective To compare the clinical effects of extensive or limited arthroscopic debridement in varying degrees of knees osteo-arthritis. Methods 32 cases with knees osteoarthritis who underwent extensive debridement under arthroscopy were selected as the observa-tion group, and 30 cases with knees osteoarthritis who underwent limited debridement were selected as the control group. The excellent rate of joint function, Lysholm and VAS scores were compared between the two groups. Results The excellent rate of joint function were 90. 0%and 91. 4% in observation group and control group respectively, without significant difference (P>0. 05). Lysholm scores of patients with grade Ⅱ osteoarthritis was much higher in observation group than that in control group after operation (P<0. 05). There was no significant difference in Lysholm scores between gradeⅠand gradeⅢosteoarthritis (P>0. 05). No statistically significant difference of VAS scores on 1 year after operation were found (P>0. 05). Conclusion Extensive debridement and limited debridement under arthroscopy have similar effects for knees osteoarthritis. Extensive arthroscopic debridement is an ideal treatment method for Ⅱ grade of knees osteoarthritis.