The deep-sea area east of Dongsha Island is chosen as the research area. The relationship between dispersion and nonlinearity is studied using nonlinear Schrödinger equation which describes deep-sea internal waves in conjuction with the idea of chirps, then the propagation of internal waves in deep sea is simulated. The numerical simulation results are found to be in good agreement with the internal wave MODIS images, which validates the rationality of simulating internal wave propagation in deep sea using nonlinear Schrödinger equation.