Abstract: Composite C-shaped flexible boom (C boom) is widely used in space field because of its light mass, simple structure and high folding ratio. In this paper, quasi-static simulation analysis of C boom was carried out by using explicit dynamics analysis method to study the mechanical properties of roll-up process, and an optimization design method of composite C boom was proposed. The geometrical parameters such as cross-section radius, cross-section centroid angle, and length of the C boom were investigated, and the effects of these parameters on the mechanical properties were investigated, such as the maximum strain energy, the first-order intrinsic frequency, and the maximum stress. Based on the response surface method, a multi-objective optimization model with maximum structural strain energy and first-order intrinsic frequency as the objective, maximum stress as the constraint, and geometrical parameters as variables was established. The feasible solution distribution and the optimal solution were obtained by using the genetic algorithm. The research results provide a certain theoretical guidance for enhancing the mechanical properties of spatial deployable structures.