Hot dip Al-Si alloy coating is an efficient corrosion resistant technology. However, there are serious Al-Si corrosion problems in some parts of the production line, such as sunk rolls, which are in direct contact with the Al-Si alloy melt. In this paper, YSZ/NiCrAlY protective coating system was prepared by air plasma spraying (APS). The influence of main gas flow on the microstructure, mechanical properties, high-temperature stability and Al-Si alloy corrosion resistance of YSZ coating were also investigated. The results showed that the spreading uniformity, coating density and mechanical properties of the droplet firstly increased and then decreased with the main gas flow rising. The coating exhibited the best surface smoothness, maximum density and optimal mechanical properties when the main flow is 40 L/min. The interface structure of YSZ coating is stable, the porosity is decreased, and the density is significantly increased after heat treatment at 1000°C for 100 h. In addition, no diffusion or reaction zone was found at the interface between YSZ coating and Al-Si alloy melt when the coated sample was immersed in the Al-Si alloy melt for 50 h. Al-Si melt did not penetrate into the coating, but was blocked on the YSZ coating surface, indicating that APS YSZ/NiCrAlY coating can effectively resist Al-Si melt corrosion, which can be used as one of the most potential protective coatings for parts contacting with high temperature Al-Si melt.