The estimation of vehicle key state which cannot be measured with ordinary vehicle-mounted sensors directly is the basic condition for vehicle motion following control. Especially, the accuracy and real time performance of the sideslip angle estimation have great influence on the control effect, which has been the focus in the vehicle state observation field. In this paper, the research status of the vehicle sideslip angle estimation methods is summarized: kinematics based method, dynamic based method, kinematics and dynamics fusion method, and multi-source sensors fusion method. The characteristic of different estimation algorithms is discussed. With new sensors equipment in intelligent vehicle such as GPS, camera and magnetometer, the new problems of the sideslip angle estimation including multi-rate sampling, measurement delay and attitude estimation are analyzed. Finally, the development trend of the sideslip angle estimation is prospected.