Many successful applications of partial differential equation（PDE） method in optical image denoising have been mentioned

however the application of PDE in sonar image denoising has been seldom studied before.Aiming at the serious noise pollution problems in sonar image

the principles of PDE used in sonar image denoising are introduced.Two PDE models

ROF model and fourth-order diffusion model are mainly discussed.Sonar images noise can be removed by processing based on these models.Simulation experiments show the effectiveness of PDE method and the property of two models has been compared.ROF model is suitable for sonar image processing under low SNR condition

while the fourth-order diffusion model can maintain image edge well under high SNR condition.But when the noise pollution is serious

its SNR after denoising become nearly 10 dB lower than the ROF model denoising method

so the fourth-order diffusion model is not conducive to sonar image processing.