A ground Hardware-in-Loop(HIL) simulation test platform is used to perform ground tests for flight control system of Unmanned Aerial Vehicle(UAV). For the purpose of such tests, a ground HIL simulation platform based on MATLAB Real-time Workspace(RTW) and real-time operating system VxWorks is designed. The mathematic model of the UAV is built, and the closed loop of the real-time system including a master computer, a control computer and a model computer is constructed. Hardware and software configuration, and also flight control laws are discussed. This platform enables the observation of system states in UAV flight process, the injection of disturbance, and online adjusting of parameters. This platform is simple but very functional, and it provides a valid way to test control laws of UAV.