Abstract: Rotor airfoil design is the foundation of helicopter rotor design, and accurate calculation of aerodynamic characteristics is the key to the design of practical engineering airfoil. In the aerodynamic characteristics design process of airfoil, the infrared imaging non-contact measurement transition test technology was used to test the free transition position of OA309 rotor airfoil in a large ?3.2 m low-speed wind tunnel, and the influence of free transition position and free transition on aerodynamic force was calculated using the Michel model. By comparing the calculation and test results of OA309 rotor airfoil, it can be seen that the transition positions captured in the calculation are basically consistent with the test results. The joint application of infrared imaging non-contact measurement transition technology and Michel model improves the calculation accuracy of rotor airfoil resistance and lays a foundation for multi-objective airfoil design.