针对美国30 m望远镜(TMT)三镜系统在工作时的特殊要求，对三镜系统的Rotator组件轴承进行了设计，提出了在载荷连续变化条件下轴系的设计方法。通过分析该系统独特的运动和受力方式并对比现有大型望远镜结构形式，确定了三排滚柱支撑的轴系方案及轴承结构参数。计算中将天顶角定义为变量，确定了轴承的最恶劣工况及此时的望远镜指向。采用了数值计算和有限元仿真的方法对这一条件下的轴承变形和应力同时进行校核，两种方法得到的结果符合得很好，证明了模型的正确性。结果表明，天顶角为0°~65°时，轴承在x、y、z方向上的变形不超过0.015 mm，轴承倾角不超过1.7×10-5 rad，满足设计要求，并留有很大裕度。

For the special requirements of Thirty Meter Telescope( TMT) from USA, the Rotator assembly of M3S for the TMT was designed，and a design method was put forward for a rotation bearing when its load was varying. By analysis of the motion and force-giving modes of the system and comparison with large photoelectric telescope,a three-row roller bearing scheme was chosen and the model of bearing was established. The zenith angle was defined as a variable, and the most serious working condition was confirmed then the telescope position was determined at this moment. The bearing deformation and stress were calculated by the numerical calculation and Finite Element Method(FEM) when the telescope was stopped at this position. Obtained results from the two methods are in good agreement, which demonstrates the accuracy of the model. Experiments indicate that the maximum axial deformation on the single roller will not exceed 0.015 mm in x, y, z directions and the angular deformation is less than 1.7×10-5 rad when the azimuth varies in 0°-65°. The result shows a enough margin for design requirements.