Abstract: Using light field Gaussian-Hermite source term expansion method to derive the nonlinear equations of one-dimensional FEL equation plus three-dimensional correction for particle and amplitude, the beam radius, Rayleigh parameters for light field, the steady-state Matlab code has been developed. The initial particle loading is consistent with each other for self-amplified spontaneous emission (SASE) single pass using new code and Genesis. The presented code is valuable for improving the X-ray FEL design.