Composite materials are widely used in civil aircraft structures because of their higher stiffness,strength and designability. Based on the design of the composite door for the wide-body aircraft,the finite element model was established.and the lay-up ratio of the composite door was optimized, which the design requirements of the stiffness and the strength are assigned as the constraints and the minimum weight is the target. The weight of the composite door is reduced by more than 10% and meets the design requirements of stiffness and strength.The research in this paper provides an effective method for weight reduction of composite air-tight doors, and provides suggestions for similar structure design.