To improve a SUV’s ride quality and mobility, etc., an electronic control unit of electronically controlled air suspensions (ECAS) was designed by using a Freescale XDT512 micro-controller, which consisted of a minimum system, a power source module, a driving module, a speed signal processing module, a double acceleration module, an analog signal processing module, a communication module and so on. The control strategy model of an ECAS system was designed by using the model-based design method, which included an auto-mode sub_model, a manual-model sub_model and a repair-mode sub_model. The height of the car can be automatically adjusted according to the speed in auto-mode, and a driver can freely set the height of the car by using a human—machine interface in manual-mode. In repair-mode, the functions of the ECAS system were disabled to prevent any unexpected action. The structural test and functional test were conducted after a set of test cases were properly designed. When fixed-point treatment was conducted, the control model was converted into an application program by using RTW technologies, and then it was integrated with low-level driven programs, the final integrated program was downloaded into the electronic control unit of an ECAS. Then vehicle experiments were carried out, the results of experiments showed that the proposed control strategy fulfilled the design requirements.