Objective:To analyze the etiology of patellofemoral pain syndrome (PFPS) in basketball players and the effect of isometric exercise of the quadriceps femoris .Methods:A total of 20 basketball players from Shanghai sports bureau with PFPS were selected as research group ,and 28 healthy player without PFPS were chosen as control group .The differences regarding the Q‐angle and the moving track of patella between the 2 groups were analyzed .The training method in the research group consisted of quadriceps femoris isometric and isotonic contraction while that in the control group was isotonic contraction .The incidence rate of patellofemoral pain during the training ,as well as the effect of two kinds of training on the quadriceps femoris , was analyzed .Results:There was no significant difference regarding Q‐angle between the 2 groups .The incidence rate of patella maltracking in the research group was higher than that in the control group(P< 0 .05) .There was no significant difference regarding the incidence rate of patellofemoral pain during the training between the two groups . There was no significant difference regarding the force change of quadriceps femoris after training between the two groups ,however ,the muscular endurance change in the research group was lower than that in the control group(P< 0 .01) .Conclusions:The occurrence of PFPS in basketball player was not significantly related to Q‐angle ,however ,it was related to patella maltracking . Comparing to the isotonic exercise ,the training method consisting of isometric and isotonic contraction can achieve a similar effort regarding muscle force ,but muscular endurance .