As a consequence of global warming,crops face more acute and more frequent high-temperature stress.Heat threatens the whole plant development,especially pollen development,which seems to be the most sensitive process in the plant life cycle.Hence,the mechanism underlying the pollen response to heat stress has become a hot topic in the field of plant biology.Recent studies have revealed that pollen has at least 4 ways to perceive the heat stress signal:calcium channels,unfolded protein response,reactive oxygen species and H2A.Z.Pollen responds to heat stress by regulating heat shock protein expression,glycol-metabolism and phytohormone level and enhancing reactive oxygen species scavenging capacity.In this review,we summarize pollen development defects under heat stress,the mechanism of pollen thermotolerance and discuss how to design the experiments to study pollen thermotolerance.The overview provides guidelines for the pollen heat response mechanism in crops.