The invention belongs to the field of image processing and computer vision, and more particularly discloses an image style transfer method based on a convolutional neural network. Based on a high-level semantic representation in the convolutional neural network, an image content model and an image style model are established, then an initial image is optimized to have a content representation similar to a content image and a style representation similar to a style image in the same convolutional neural network, an image fused with the content of the content image and the style of the style image is therefore generated, and the style transfer function is realized. The method of the invention can achieve style transfer for any style image.