Objective To investigate the apoptosis of neurons and the change in the expression of caspase-3 in rat cerebral cortex induced by heat stress.Methods Wistar rats were randomly divided into normal control group and heat stress group. The rats in the normal control group were placed in an environment with a temperature of (25±0.5)℃ and a relative humidity of 35%±5%, and those in the heat stress group were placed in a chamber with a temperature of (40±0.5)℃ and a relative humidity of 60%±5% for 100 minutes. TUNEL staining was used to observe the apoptosis of neurons in rat cerebral cortex, and immunohistochemistry and quantitative real-time PCR were used to measure the expression of caspase-3 in neurons.Results The apoptosis of cerebral cortex neurons appeared at 1 day after heat stress and reached the peak at 3 days. Caspase-3 expression appeared at 2 days after heat stress and reached its peak at 3 days. Quantitative real-time PCR showed that there was a significant difference in the content of caspase-3 at 1, 2, 3, and 7 days between the heat stress group and the normal control group, and the heat stress group had the highest content of caspase-3 at 3 days.Conclusions Heat stress can activate the expression of caspase-3 and induce apoptosis of cerebral cortex neurons.