The use of a helicopter is an expected novel method for Martian geological exploration. We developed a blade element theory combined with two-dimensional computational fluid dynamics, which is a method to evaluate rotors with high fidelity and low cost, to design rotors with sufficient flight performance on Mars. The proposed evaluation method agrees with the experiment under low Reynolds number. In this paper, it is carried out a rotor blade optimum design based on genetic algorithm using the proposed method for performance evaluation. The optimum solution was compared with typical airfoil with good performance under low Reynolds number and carries out knowledge acquisition of designing rotor blade.