Three error estimation criteria for solving nonlinear transmission equation of multimode fiber— max, sum and ave criterion are proposed. The multimode error vector is converted to the error scalar, and the adaptive step size uniform change of multi-mode is realized based on the local error method of symmetric split-step Fourier. By simulating the transmission of Gaussian pulse in the graded-index multimode fiber, the performance of local error and global error of the fixed-step and variable-step method in different criteria are verified. The experimental results show that all the variable step size algorithms of the three criteria are convergent, besides, using the sum criterion calculate local error to control step size change can obtain higher numerical precision under the same calculation amount, and in the case of the same global error, the calculation amount is relatively less. The study is of significance for further improving the computational efficiency of multimode nonlinear transmission equations.