Abstract: Structures used in aerospace are influenced by temperature. So coefficient of thermal expansion (CTE) is not only an important parameter of materials, but also a significant parameter of structural design of spacecrafts with high dimensional stability. In this paper, based on the analysis of the data from tests, theoretical formulae for predicting CTE and mechanical properties of hybrid composites are presented, and the calculation program is compiled. All the equations are verified by experiments. Optimization is conducted by computer. The results and methods presented in this paper can be used both in optimal design of hybrid composites with zero CTE and in design of hybrid composites with any certain CTE value