The physical mechanism of “shock cooling” at the molecular fluid/window interface has troubled the shock wave physics community for many years and remains unsolved. There are three distinct viewpoints for explaining the cooling effect at the shock interface: thermal equilibrium between the molecular fluid and the window, extinction effect of the molten optical window, and specific shock response of the molecular fluid. This paper comparatively investigates the shock radiation and temperature variation characteristics of the interfaces between the chemically active fluid CHBr₃/the inert liquid argon (LAr) and the LiF optical window. Under the same shock pressure, the interface radiation exhibits distinct evolution features for the two liquids, indicating that the interface cooling effect is closely related to the fluid medium and its chemical activity. Therefore, the experimental results of this paper strongly support that the interface cooling effect is caused by the shock response of the fluid itself, rather than heat conduction or window melting extinction.