Objective:To determine the role of the parathyroid hormone (PTH) in fracture healing of mice. Methods:A total of 30 male mice at 8 weeks old (including 15 wild-type mice and 15 PTH gene knockout mice) were selected to establish right femur fracture model. At 7,14 and 21 days after the operation,the mice were sacrificed for measurement of bone mineral density (BMD) of the callus by micro-CT. To determine the role of PTH in fracture healing,the fracture models were assessed by histology,immunohistochemistry,X ray and micro-CT. Results:At 14 and 21 days after the operation,BMD in PTH gene knockout mice was significantly reduced compared to that in PTH wild-type mice (P < 0.05). X ray and micro-CT scanning showed that the fracture healing and the callus transformation and remodeling in PTH gene knockout mice were both delayed compared to those in wild-type mice. Conclusion:This study suggests that endogenous PTH promotes the fracture healing in mice.