According to the problem of the strong background noise and edge blur in intravascular ultrasound(IVUS) images, an improved anisotropic diffusion is proposed. Firstly, median filter is imported to the PM algorithm, and then the gradient mode of the original image is replaced with the gradient mode from the image which is smoothed by the median filter to control the process of diffusion. Secondly, the direction of the conventional diffusion anisotropic diffusion equation is extended from 4 directions into 8 directions to retain more image details. Thirdly, a method of adaptive selection of the diffusion threshold K is put forward. The experimental results show that the improved algorithm has a satisfactory effect in removing noise and preserving edge, and providing a basis for the edge extraction of intravascular ultrasound images.