In this study, the functional safety attributes of vehicle steering system are examined and a real vehicle test method is proposed based on a whole vehicle in the loop (VIL) platform. By analyzing the general framework of the steering control system, extracting the limit test scenarios from road test conditions for transformation research and then applying it to the whole vehicle in the loop simulation test platform based on steerable axle coupling dynamometer, and conducting real vehicle level testing, the results of functional safety are analyzed in depth. Furthermore, the evaluation index system of extreme working conditions is established. The results of this study provide a comprehensive reference method for steering functional safety testing and evaluation that can be used by vehicle manufacturers and research institutions.