60vol %Carbon fiber reinforced magnesium matrix composites were fabricated by pressure infiltration method. The coefficient of thermal expansion measurement of carbon fiber reinforced magnesium matrix composites were carried out on a dilatometer 402C at the temperature ranged at 20~300 ℃. The relations among α and heat treatment condition, elastic modulus of the fibers and yield strength of matrix alloys were investigated. Results showed that α of the composites decreased with increasing of elastic modulus of fibers and reducing of yield strength for matrix alloys. Moreover, the α of composites decreased after annealing treatment. In this paper, the estimate formula of the α in transverse direction of composites is presented, and this calculation method should minimize the error between the calculation value and the true value. The model for laminate structure composite α in 2D planar is suggested, and the α of [0/±15/±30/±45/±60/±75/±90]S laminates are isotropy.