A design method of composite materials and metals embedded with each other was put forward. On the basis of the space layout of optical elements in a coaxil three-mirror optical system and the technological properties and attributes of the Carbon Fiber Reinfored Plastic(CFRP), the main backbone of the camera was designed and manufactured with CRFP and titanium by this method. First, the core body of main backbone was made up of CFRP, and the gridding and thickness were optimized with topology analysis. Then, the metal embedded parts were arranged according to an optical lens, every metal embedded parts were lightweighted and the mode and the deformation of the main backbone were analyzed. Finally, the results of design and analysis were verified by a vibration test. The experiment and test indicate that the CFRP main backbone is 15.6 kg , the circumscribed circle diameter is Φ870 mm,and the height is 130 mm.Furthermore, the average density and the first mode frequency are 0.313 g/cm2 and 479.2 Hz,respectively. These results prove that the CFRP main backbone can meet the requirements of light weight,high dynamic stability and good surface precision for space cameras.