Objective To evaluate the effectiveness of open reduction and trans-carpometacarpal joint internal fixation with mini locked-plate for treatment of comminuted fracture of base of the fifth metacarpal. Methods Between July 2015 and December 2017, 8 cases of comminuted fractures of base of the fifth metacarpals were treated with open reduction and trans-carpometacarpal joint internal fixation with mini locked-plate. There were 7 males and 1 female with an age of 19-45 years (mean, 32.5 years). The causes of injury included 2 cases of hitting hard objects while clenching fist, 6 cases of falling injury. There were 2 cases of subluxation of fifth carpal joints and 1 case of dislocation. The time from injury to operation was 1-5 days (mean, 3.5 days). The stability of fracture ends could not be maintained by preoperative evaluation without over articular fixation or short time over articular fixation. Postoperative complications and fracture healing were observed, and hand function was evaluated at last follow-up according to the total active motion (TAM) recommended by the Branch of Hand Surgery of Chinese Medicine Association. Results All the incisions healed by first intention without complications such as wound infection, cutaneous necrosis, tendon or nerve injury. All the patients were followed up 6-18 months (mean, 12 months). All fractures healed with the healing time of 12-16 weeks (mean, 13 weeks). Within 4 months after operation, all patients were able to return to pre-injury job. At last follow-up, according to the TAM recommended by the Branch of Hand Surgery of Chinese Medicine Association, the results were excellent in 7 cases, good in 1 case, with the excellent and good rate of 100%. Conclusion Applying of mini locked-plate for treatment of comminuted fractures of base of the fifth metacarpal, of which cannot obtain stable fixation through non-transarticular or short-time transarticular fixation, can achieve satisfactory functional results with very few complications through trans-carpometacarpal joint approach, thus the procedure can be used as an alternative operation scheme.