Abstract: Since it is hard to design the truss structure in space camera which has both low weight and high stiffness, the rule of full stress is proposed to optimize the truss section. The design rule and request of the optical system are introduced. By selecting the truss weight as the optimization object, gravitation transmutation and first frequency of secondary mirror as the restriction condition, and the inside and outside diameters of truss section as the optimization variables, the optimization model based on full stress rule is established. The optimized inside and outside diameters of truss section are 40mm and 50mm respectively, the optimized weight of truss is 6.3kg, while the first frequency is 121Hz. The mode analysis, gravitation transmutation analysis and temperature raise of 15℃ analysis later indicate that the truss optimized can satisfy the needs of the optical system. Finally, 0.2g vibration test and dimensional stability test are inflicted to the truss, which shows that the first frequency of the truss is 119Hz, and that the transmutation of the secondary mirror is less than 5". The truss optimized has the characteristic of compact structure and fine dimensional stability which meet the needs of space camera well. It lays a foundation for development of space camera with large caliber, long focus and light weight.