Abstract: A method was proposed for designing and optimizing composite shaft and a mathematical modal was established based on it. In the model, the quantity was set as objective, and the strength, critical speed and the outer diameter dimensions were set as restraint conditions. The design parameters consist of the thickness of the core, number of composite layers, thickness of single layer and the fiber's direction of each layer. A design and optimization platform was also established by ANSYS for optimizing both the discrete variables and the continuous variables. A low pressure turbine shaft was taken as a design example using metal matrix composite. It can save 36.16% mass compared with the metal one.