目的　观察正常人成纤维细胞体外培养过程中超微结构的变化规律。方法　将正常人二倍体成纤维细胞进行传代培养 ,以不同代次的细胞为实验对象 ,通过倒置相差显微镜与透射电镜对各代细胞进行了观察。结果　 4 5代以内的细胞生长较迅速 ,4 5代后的细胞生长逐渐缓慢 ,6 5代细胞几乎无增殖趋势。 4 0代以内细胞的超微结构无明显变化 ,4 1～ 6 5代细胞出现核膜内折 ,细胞核 浆比例减小 ,细胞表面突起和微绒毛减少。结论　各代成纤维细胞超微结构改变程度不同 ,4 1代后变化明显。 Objective To observe the ultrastructural changes of normal human fibroblasts cultured in vitro. Methods Normal human diploid fibroblasts were subcultured, and different generations of cells were used as experimental subjects. The cells of all generations were observed by inverted phase contrast microscope and transmission electron microscope. Results The cells within 45 generations were rapidly growing, the cells growing after 45 generations were gradually slowed down, and there was almost no proliferation tendency in 65 generations. There was no significant change in the ultrastructure of the cells within 40 generations, 4 to 6 ~ 5 generations of cells appeared nuclear membrane fold, the proportion of nuclear cytoplasm decreased, cell surface protrusions and microvilli decreased. Conclusion The ultrastructural changes of fibroblasts in different generations are different, and their changes after 4 generations are obvious.