We describe a new model and use MATLAB simulation to numerically analyze the multi-mode dynamics of the semiconductor laser.The active modes are coupled by a set of rate equations,where we take into account two types of mode-mode coupling:(i)carrier sharing and(ii)mutual coherent optical injection via multi-wave mixing.Our numerical analysis of mode interaction provides a detail simulation results of the laser in terms of output power and uses Fast Fourier Transform(FFT)to get optical spectra of the electric field,from which we get the side mode suppression ratio.The simulation is operated under different conditions,i.e.different line width factor,different mode spacing,and varying the pump current for one mode,two-mode and three-mode cases.