Objective To explore the feasibility and short-term effectiveness of the modified radical resection and reconstruction in the treatment of malignant proximal humerus tumor. Methods The relevant anatomic data from 30 normal adult shoulder joint MRI were measured to analyze the feasibility of modified radical resection and reconstruction surgery in the treatment of malignant proximal humerus tumor. Five patients with malignant proximal humerus tumor were treated by using the modified radical resection and reconstruction surgery between March 2012 and January 2016. There were 1 male and 4 females, aged from 9 to 69 years (median, 46 years). There were 4 cases of osteosarcoma (Enneking IIA in 2 cases and Enneking IIB in 2 cases) and 1 case of metastatic carcinoma (moderately differentiated adenocarcinoma). The disease duration was 7 to 12 months (mean, 9 months). Recurrence of tumor was observed after operation, and the shoulder function was assessed according to Enneking skeletal muscle tumor function scoring system. Results Radiographic results showed that modified radical resection and reconstruction surgery was feasible, which was in allowable range of the maximum longitudinal diameter ( < 29.8 mm) and depth ( < 4 mm). The operation was successfully completed in all 5 cases, and pathological examination suggested that purposes of radical resection had achieved. All patients were followed up 3 to 49 months (mean, 15.6 months). One patient had local recurrence at 12 months after operation, and a shoulder joint amputation was performed; the other 4 patients had good prosthesis survival. At last follow-up, the function of the shoulder joint was obviously recovered when compared with preoperative function; Enneking's skeletal muscle tumor function score was 25.8 points (range, 24 to 27 points). Conclusion Modified radical resection and reconstruction surgery is feasible for the treatment of proximal humerus tumor, and it can maintain a good early shoulder function.