<p>To study the effect of impact orientation on droplet spread and breakup during droplet impact droplet adhering to an inclined surface, a 3D two-phase flow numerical model based on the coupled level set and volume of fluid method was established. The influence of droplet size and airflow velocity on droplet dynamics during impact was studied. Four spread factors were defined to evaluate the wetting effect. When the impact occurs at the upstream point, a low-pressure zone and a counterclockwise air vortex form around the droplet. The increase in airflow velocity and droplet size leads to a greater tendency for the liquid film to break apart, making the spread effect more pronounced. At the impact centre, a low-pressure area and a counterclockwise air vortex exist at the edge of the liquid film. The increase in airflow velocity enlarges the area of liquid film breakup, while the increase in droplet size reduces the height of the liquid film impact. When the impact occurs at the downstream point, the expansion of the downstream liquid film decreases the negative pressure zone and the air vortex above. The increase in airflow velocity enhances spread at the downstream end, and the increase in droplet size increases the breakup extent of the downstream liquid film.</p>