Abstract: The interfacial wettability and heat transfer behavior are crucial in the strip casting of high phosphorus-containing steel. A high-temperature simulation of strip casting was conducted using the droplet solidification technique with the aims to reveal the effects of phosphorus content on interfacial wettability, deposited film, and interfacial heat transfer behavior. Results showed that when the phosphorus content increased from 0.014wt% to 0.406wt%, the mushy zone enlarged, the complete solidification temperature delayed from 1518.3 to 1459.4°C, the final contact angle decreased from 118.4° to 102.8°, indicating improved interfacial contact, and the maximum heat flux increased from 6.9 to 9.2 MW/m². Increasing the phosphorus content from 0.081wt% to 0.406wt% also accelerated the film deposition rate from 1.57 to 1.73 μm per test, resulting in a thickened naturally deposited film with increased thermal resistance that advanced the transition point of heat transfer from the fifth experiment to the third experiment.