To provide a better image deblurring and remove successfully the speckle noise, a novel PDEbased image denoising approach is proposed in this paper. It is based on a nonlinear fourthorder diffusion model. The nonlinear PDE scheme is described first. Then, a mathematical treatment is provided for this differential model, its wellposedness being investigated. It is proved that the model is wellposed in some certain conditions and admits a weak solution. The weak solution of the obtained PDE is approximated by developing an explicit finitedifference based numerical discretization scheme. The experimental results show that the new model proposed in this paper can achieve good results in image denoising and preserving edges and other details. Compared with the classical model, the peak signal to noise ratio is greatly improved and the denoising performance is more better.