Abstract: Objective To investigate pathological changes in cat brain tissues after gunshot wound in the head in hot and humid environments. Methods Sixteen cats were randomly divided into 4 groups, namely the normal environment (group 1), gunshot in normal environment (group 2), hot and humid environment (group 3), and gunshot wound in hot and humid environment (group 4) groups. Pathologicol changes of the cat brain tissues were observed with both optical and electron microscopes. Results The early-stage changes in group 2 were high-lighted by vasomotor dysfunction, with the coexistence of both vascular spasm and dilation. In group 3, vascular spasm was depressed while hemorrhagic changes increased. On the brain tissue sections in group 4 for optical microscopic observation and ultra-thin sections for electron microscopic examination, the number of viable neural cells was obviously reduced, and edema, degeneration of the organelle occurred; loosening of the capillary tight junction, rupture and bleeding of the blood vessels, as well as degeneration and loosening of the myelin sheath were observed by transmission and scanning electron microscopes, and such changes were more serious than those in group 2. Conclusion The hot and humid environment can significantly affect the pathological changes in the brain tissues of cat with cranial gunshot wound.