目的探讨毛细胞白血病（HCL）超微结构诊断特征。方法利用透射电镜观察7例HCL患者外周血或骨髓中毛细胞的超微结构特征。结果电镜下可见毛细胞，其超微结构特点是：①微绒毛特点：数量多、微绒毛长、粗细相同、形态各样；②胞核特点：卵圆形，稍有刻痕，异染色质沿核膜内面分布；③胞质特点：细胞器丰富，首次发现髓鞘结构小体，但未见核糖体板层复合体。结论毛细胞的微绒毛特点是HCL超微结构诊断的重要特征，胞核和胞质特点可用做HCL鉴别诊断的参考特征，核糖体板层复合体不一定是HCL的诊断特征。 Objective To investigate the ultrastructural features of hairy cell leukemia (HCL). Methods Transmission electron microscopy was used to observe ultrastructure of hair cells in peripheral blood or bone marrow of 7 patients with HCL. RESULTS: Hair cells were observed under electron microscope. The ultrastructural characteristics were as follows: 1 microvilli characteristics: large numbers, microvilli, length, thickness, and shape; 2 nuclear characteristics: oval, slightly nicked, heterochromatin Distribution along the inner surface of the nuclear membrane; 3 cytoplasmic characteristics: organelles rich, first discovered myelin structural body, but no ribosomal lamellar complex. Conclusion The characteristics of microvilli of hair cells are important features of the ultrastructural diagnosis of HCL. The features of nucleus and cytoplasm can be used as reference features for the differential diagnosis of HCL. The ribosome lamellar complex is not necessarily the diagnostic feature of HCL.