In order to improve the positioning accuracy of mobile robots, a kind of positioning system for wheeled mobile robots based on orthogonal encoder and gyroscope was proposed, and the positioning model and kinematics model of robot were established. With the purpose of obtaining better robustness, Support Vector Regression (SVR) algorithm was studied, the error square of objective function was weighted, and the effect of different parameter optimization algorithms on the accuracy of SVR were analyzed. The experimental platform was established by homemade mobile robot, the Least Squares Support Vector Regression (LSSVR) algorithm and the Weighted Least Squares Support Vector Regression (WLSSVR) algorithm were compared with the improved algorithm. The positioning errors of the improved algorithm when the robot worked on ceramic and wood floor were compared, and the orthogonal encoder plus gyroscope positioning system was compared with the double encoder positioning system and the single encoder plus gyroscope positioning system. The experimental results show that the robot positioning accuracy of the improved algorithm is higher than comparison algorithms, and the proposed positioning system has a better location performance.