Automatic recognition of the number of instruments for automatic detection and automatic control is of great significance, this paper to the automatic identification of the number of disc instrument as the research content. An automatic recognition method based on Snake algorithm is proposed, which is divided into three parts. The first link, using Hough transform to disc instrument for rough positioning of circular feature; the second link, the snake algorithm on disc instrument circular features accurate positioning; the third link by Hough transform to pointer and scale linear feature location. According to the experimental study of the pressure gauge image, the experimental results confirm the validity of the automatic recognition method based on the Snake algorithm.