Octagonal tubes are commonly used type of profile in mechanical manufacturing. They have broad application prospects in aviation, rail transportation, robot frames, and medical devices. Preparing uniform wear-resistant and corrosion-resistant coatings on their surfaces is an important method to prevent their failure. High velocity air-fuel (HVAF) thermal spraying has the characteristics of high kinetic energy and low thermal load and is an important process method for preparing high-performance coatings. Achieving process control and shape control in HVAF supersonic spraying for octagonal tube parts is a bottleneck problem in the industry. This study establishes a numerical model of the HVAF supersonic spraying process for octagonal tube parts based on the computational fluid dynamics (CFD) method, and conducts a full-cycle analysis for the combustion reaction, flame jetting and turbulent state, and particle flight characteristics during the spraying process. It systematically investigates the influence of key process parameters on HVAF spraying behavior. The influence of preheating temperature, particle injection velocity, and N2 mass flow rate on flame flow characteristics and particle flight behavior are analyzed in detail. A strong mapping relationship between optimal particle flight state and process parameters is established, providing a theoretical basis for effectively controlling the spraying quality and optimizing the process. This study conducted systematic numerical simulations, providing theoretical guidance for the optimization of spraying process parameters.