目的：探讨骨折愈合过程中 Ｐ２１ｒａｓ对细胞增殖分化的调控作用。方法：建立颌骨骨折模型，利用免疫组化法观察颌骨骨折愈合的不同阶段 Ｐ２１ｒａｓ的表达。结果：骨折愈合早期（第１～５ ｄ）仅见少量 Ｐ２１ｒａｓ阳性细胞；而骨痂形成期（第７～１４ ｄ）骨断端附近的阳性细胞数量和染色强度明显增加；骨改建期（第２１～２８ ｄ）阳性细胞数量和强度均减少，与正常骨基本相同。结论： Ｐ２１ｒａｓ参与了骨折愈合过程中细胞的增殖和分化。 Objective: To investigate the regulatory effect of P21ras on cell proliferation and differentiation during fracture healing. Methods: The jaw fracture model was established. The expression of P21ras at different stages of fracture healing was observed by immunohistochemistry. Results: Only a small amount of P21ras positive cells were seen in the early stage of fracture healing (from day 1 to 5), while the number of positive cells and the staining intensity were significantly increased in the period of callus formation (from day 7 to 14) ~ 28 d) the number and intensity of positive cells decreased, with the same basic bone. Conclusion: P21ras is involved in the proliferation and differentiation of cells during fracture healing.