Objective To investigate the preparation of Al₂O₃ -TiB₂ -Al composite coating on the aluminum alloy surface, and analyze the reaction mechanism of Al, TiO₂, B₂O₃in plasma spraying. Methods The composite coating was prepared on the surface of aluminum alloy using plasma spraying technology. The phase composition and microstructure evaluation of composite coating layer were analyzed by scanning electron microscopy ( SEM) and X-ray diffraction technology. The combustion products of combustion front quenching technique were tested. Results It was found that the activation energy of the powder reaction was effectively decreased by mechanical milling, and the optimal flying distance range of plasma spraying was 150 ~ 200 mm. Conclusion According to the results, the composite powder experienced the processes of preheating, melting, decomposition and agglomeration during the flight, which verified the mechanism of combustion reaction.