现代空间光学遥感器向着大口径、长焦距的方向发展。焦距变长意味着主次镜间隔变长，也就意味着次镜的系统公差更难保证。针对次镜严格的公差要求，本文提出了一种空间桁架结构的设计理念。根据静定空间桁架原理，设计了两种结构方案，采用有限元分析软件，对两种方案进行了分析，求得前三阶固有频率、绕X 轴的倾角和Y 方向刚体位移。分析结果表明，设计方案1 的一阶模态为78 Hz，绕X 轴的倾角为2″，沿Y 轴的最大刚体位移是0.04 mm；设计方案2 的一阶模态为113.7 Hz，绕X 轴的倾角为1.5″，沿Y 轴的最大刚体位移是0.022 mm。两种方案都能满足设计要求，而方案2 比方案1 有明显优势。静定空间桁架原理为空间相机结构设计提供了可靠的理论依据。

The way of development of modern space optical sensors is large aperture and long focus length. Long focus length means the distance between primary and secondary mirror will be longer, and tolerance of secondary mirror means more difficult to guarantee. For the secondary mirror strict tolerances, a design of space truss structure is presented. According to the theory of statically determinate spatial frameworks, two schemes are designed and were analyzed through finite element analysis software. We got the first three inherent frequencies, the angle around the X axis and the rigid body displacement along Y axis. The results show that the first mode of the scheme 1 is 78 Hz, the angle around the X axis is 2″, and the largest rigid body displacement along the Y axis is 0.04 mm. For scheme 2, the first mode is 113.7 Hz, the angle around the X axis is 1.5″, and the largest rigid body displacement along the Y axis is 0.022 mm. Two schemes can meet the design requirements, while scheme 2 is more excellent than scheme 1. The theory of statically determinate spatial frameworks provides a reliable theoretical basis for the structural design of space camera.