Abstract: With the advantages of low cost, reducing risk, configurable test conditions, and accurate test data, low speed wind tunnel free-flight test technique has become an important method to support the development of aircraft with radical configuration and new technology. As the core-system of the wind tunnel free-flight test platform, the flight control system should satisfy similarity criteria to ensure that the test results represent the stability and control characteristics of prototype aircraft. Based on the similarity criteria, the similarity requirements and simulation methods of the flight control system were analyzed. We discussed the problems of similarity conversion of the flight control law, the determination of the system sampling frequency, and the impact of performance of onboard sensors and actuators on aircraft response. A wind tunnel free-flight test has been conducted to verify the feasibility of the system implementation and the accuracy of the test results in predicting stability and control characteristics of the prototype aircraft. The research established a foundation for the improvement of the test technique and the promotion of its industrial application.