Abstract: The introduction of alloy melts into the pores of C/C composites at high temperatures and the in situ reaction with pre-deposited matrix materials, resulting in the formation of ultrahigh-temperature ceramics with high strength, high melting point, and excellent thermal conductivity, is of great significance for today's increasingly stringent performance demands for high-temperature and thermal protection materials as science and technology are changing day by day. This chapter focuses on the wettability of (Ti, Zr, Hf, Si) high temperature alloys, using the seat-drop method as the testing principle and the YG0020-2300 ultra-high-temperature melt surface tension wettability meter to measure the wettability of multi-alloy melts on pyrolyzed carbon materials, aiming to analyze the influencing factors and the intrinsic mechanism of the wettability in depth. The results show that the wetting angle is only 0.58585422° when the atomic ratio of Ti: Zr: Hf: Si is 3: 12: 4: 2, and then the Ti-Zr-Hf-Si alloy melt has the best wetting performance.