Objective To observe the early postnatal long bone development in Fgfr2+/S252W mutant mice and littermate wild-type (WT) mice, and explore the effect of continued function enhancement of fibroblast growth factor receptor 2 (FGFR2) gene on endochondral ossification. Methods A mouse model of Fgfr2+/S252W simulated human Apert syndrome was reproduced by knock-in technique, and then the gain-of-function mutation Fgfr2+/S252W mice and littermate WT mice were obtained after breeding and identification. Three Fgfr2+/S252W and same number of WT mice were sacrificed at 7, 10, 14 and 28 postnatal days respectively, and the morphology of long bone was examined with X-ray and Micro CT, the structure of bone and cartilage was observed by HE staining, and the expression of gene in growth plate was observed by immunohistochemical analysis. Results Fgfr2+/S252W mouse model exhibited typical craniosynostosis and brachycephalium of Apert syndrome, accompanied by short stature, growth retardation of long bone, delayed appearance of secondary ossification center, decrease of bone density and trabecula number. HE staining showed noticeable shortened zones of proliferation and hypertrophic chondrocytes, irregularity of cell arrangement, and small hypertrophic chondrocytes in the growth plates of the mutant mice. Immunohistochemical analysis revealed that the expression of genes related to chondrocytes proliferation and differentiation was decreased in mutant mice. Conclusions Gain-of-function mutation in FGFR2 may lead to abnormal development of long bone in mice. FGFR2 may have the function of regulating the development both of osteoblast and chondrocyte lineages, and play an important role in the process of skeletal development.