This paper put forward an adaptive threshold image denoising algorithm based on fitting diffusion to deal with the problem of texture loss and edge degradation. The algorithm will first improve the diffusion coefficient of the diffusion equation, establish fitting diffusion coefficient, avoid filtering incomplete due to the rapid convergence and the problem of image excessive smoothing. Then, the threshold will be designed and improved, and it will be automatically controlled by the maximal image gray value and iterative times, which can keep the image edge and detail features. Last, the designed algorithm will be simulated. The experimental result shows that the proposed algorithm can enhance the performance of denoising and protection of edge and detail information of texture, the peak Signal to Noise Ratio is promoted drastically. The new algorithm has excellent performance and is beneficial to practical application.