齿轮（齿轴）是风能发电机组上非常重要的结构件。对齿轮的主要失效形式及其特征做了介绍。从齿轮正常服役时的受力特点、选材特点、工艺特点以及使用特点等几个方面论述了齿轮失效的内在原因和外部原因。结合实际案例分析，对经常失效的风能发电机组上齿轮（齿轴）的失效原因做了归纳，发现疲劳断裂和氢脆型断裂是其最常见的失效形式，材料的冶金质量是目前国产风能发电机组上齿轮（齿轴）发生失效的主要原因，提出了风能发电机组上齿轮（齿轴）失效的预防措施。

Gears (gear shafts) are very important structural components on wind turbines. The main failure modes of the gears and their characteristics were introduced. The internal and external causes of gear failure were discussed from the aspects of the force characteristics, material selection characteristics, process characteristics and use characteristics of the gear during normal service. Combined with the actual case analysis, the failure causes of the gears (gear shafts) of the frequently-failed wind turbine generators were summarized. It is found that fatigue fracture and hydrogen induced cracking are the most common failure modes. The metallurgical quality of the materials is the main reason for the failure of the gear (gear shafts) on the domestic wind turbine generator systems, and the preventive measures for the failure of the gear (gear shafts) on the wind turbine generator systems are proposed.