The rotor blade finite element dynamic model and fatigue life model is derived from Hamilton theory. The section stiffness of flapping, lagging and pitching, linear density of blade section are used as design variables, constrains on frequency placement, autorotational inertia are included, the objective function is to minimize the blade mass and maximize the fatigue life. The optimization is realized by using the Satisficing Trade-off Analysis. Finally, compared with the optimization result of the designed model, the result shows that the optimum solution results in a 7.27 percent reduction of the total rotor blade mass and the fatigue life for the optimal design is 4.73 108 times form the initialized design 3.98 108 times, increase of 18.7 percent, under the control of the constrained conditions , perturbation of design variables and dynamics characteristics.