The problem of poor convergence is existed when arbitrary initial values for Stokes-waves power are employed in the process of numerical mode which the output characteristics of multi-order cascaded Raman fiber lasers using shooting method directly to solve the nonlinear coupled equations used to describe stimulated Raman scattering in fibers.A method of adopting genetic algorithm to determine the region of convergence for the initial values at first,and then solve the coupled equations by Runge-Kutta method and shooting method fast and efficiently is proposed.The effects of fiber length,reflectivity of output coupler and pump power on the output characteristics of a 6th-order cascaded Raman fiber laser are studied on the basis of the proposed method.