Objective: To investigate the effect of six-step upper limb exercises on the incidence of catheter-related thrombosis (CRT) in breast cancer patients undergoing peripherally inserted central catheter (PICC) chemotherapy. Methods: A total of 151 breast cancer patients undergoing PICC chemotherapy in our department from September 2017 to April 2018 were randomly divided into two groups: 76 patients in the control group were given routine fist-clenching exercise, and 75 patients in the observation group were given six-step upper limb exercises. The basilic vein, subclavian vein, innominate vein and axillary vein were examined by color Doppler ultrasonography at 1 week, 4 weeks, 8 weeks and 12 weeks after catheterization. The incidence of thrombosis in the three groups was compared. Results: The incidence of CRT in the first week, the fourth week and the whole group of patients in the observation group was significantly lower than that in the control group. There was no significant difference in the incidence of new CRT in the eighth and twelfth weeks after catheterization. In patients with CRT, the stenosis degree of CRT in the control group was significantly higher than that in the observation group (P<0.05). Conclusion: Six-step upper limb exercises can effectively reduce the incidence of PICC catheter-related thrombosis in breast cancer patients undergoing chemotherapy, which is worthy of further promotion in clinical practice.