Abstract: This paper reviewed the intrinsic mechanisms through which heat stress affected reproductive performance in dairy cows,scientific assessment methods,and integrated mitigation strategies.It provided an in-depth analysis of the physiological and molecular mechanisms by which heat stress impairs fertility through multiple pathways,including inducing oxidative stress,disrupting endocrine homeostasis,impairing oocyte quality and embryonic development,and interfering with epigenetic programming.The paper explored heat stress assessment systems based on the temperature-humidity index,physiological indicators （such as rectal temperature and respiratory rate）,and behavioral changes,and analyzed their associations with key reproductive traits such as conception rate and the interval to first postpartum ovulation.It comprehensively reviewed current research progress and the potential of strategies to mitigate the negative effects of heat stress,including genetic selection,precise nutritional regulation,environmental improvements,and emerging biotechnologies,offering theoretical foundations and practical guidance for dairy farms to establish efficient heat stress response systems and enhance reproductive efficiency.

Key words: heat stress, dairy cow, reproductive performance, temperature-humidity index, oxidative stress, epigenetics, mitigation strategy