In this paper, a protective structure for the thermometer probe was designed aiming at the infrared temperature measurement requirements of the high-temperature cascade test bench. The requirements of thermal protection and pollution protection for the thermometer probe can be achieved without interfering with the mainstream as much as possible. The rationality of the structural design was analyzed through CFD calculations and the impact of total pressure at the cooling air inlet was also analyzed in this paper. The results indicate that: the low total pressure of inlet can cause high-temperature ablation of the probe, while a high total pressure will cause significant interference with the mainstream. Finally, the inlet flow rate of the cooling water was analyzed. The results showed that the cooling performance of the probe increased with the increase of flow rate. When the flow rate was greater than 2 m/s, the cooling performance remained basically unchanged with the change of flow rate.