Abstract: In order to explore the odometer implementation method based on image sonar, the odometer method based on optical images is taken as a reference in this paper. On this basis, the original optical linear projection model is improved into a more accurate nonlinear "projection" model, making it more suitable for sonar images. The idea of realizing sonar odometer is proposed from sonar image to feature detection, feature matching, motion estimation and finally getting sonar odometer. For the problem of scale invariant feature matching, combined with the characteristics of low sonar image resolution and low signal to noise ratio, a more robust matching method is proposed, which effectively reduces the occurrence frequency of abnormal matching of feature points. Semi-physical simulation experiments verify that the sonar motion trajectory can be effectively obtained by this method, which provides a reference for the study of odometer based on image sonar.