Abstract: In order to design energy-absorption tubes for different impact loadings, the dynamic fracture process of composite tubes under axial crash loads was simulated by nonlinear explicit finite element method. The orthotropic material constants for fiber-reinforced polymer were obtained based on the strength and stiffness theory of composites. According to the principle of orthogonal design, the nonlinear mapping relations between specific energy absorption of tubes and their geometry parameters were established, and corresponding response surfaces were constructed. With the restriction of peak acceleration in frontal vehicle collision, the structural parameters of tubes with high specific energy absorption and low peak impact force were optimized by using sequential quadratic programming algorithm. The simulation results show that the deformation modes, absorbed energy, impact force versus displacement curve as well as the peak impact load agree well with that of experiments. The obtained maximum special energy absorption is 29.231 J/g when the wall thickness, edge length and tube length of square tube are 2.1, 44 and 200 mm, respectively.