The rotor airfoil has i mportant influence on aerodynamic characteristics of helicopter and its rotor. I ncorporating with the flight characters of helicopter and aerodynamic circumstan ce of helicopter rotor, a new design concept of rotor airfoil is proposed, which is the optimization design method considering both steady and unsteady states for helicopter rotor airfoil design. Firstly, the high accuracy CFD method is establish ed to simulate the unsteady aerodynamic characteristics of rotor airfoil. Consid ering the characters of optimization conditionfor rotor airfoil, the genetic alg orithm (GA) and the sequential quadratic programming (SQP) method are employed in stea dy optimization and unsteady optimization process respectively. In order to obta in an initial airfoil, the optimization design is firstly accomplished under ste ady condition. Then the optimization design under unsteady condition is implemen ted to form a new airfoil with unconventional configuration which is suitable as the rotor airfoil. The optimized airfoil has remarkable improvements on dynamic stall characteristics with obviously weakened separated vortex while it maintai ns considerable aerodynamic characteristics of steady condition.