Abstract: High temperature -caused heat stress has become a main limiting factor for production of cucumber(Cucumis sativus L.) in summer. Heat stress not only leads to early senescence of plants, hence shortened reproductive period, but also results in weakening plant disease resistance and reducing quality of produce. Improving heat stress resistance of cucumber is a challenge in the current cucumber breeding research. Here we reviewed the physiological consequences when heat stress prevailed, and identified genetic traits for such physiological responses and the molecular mechanisms for heat stress tolerance in cucumber. An understanding of the physiological and genetic mechanisms of heat tolerance is the basis of the breeding and hope this review can contribute to the cucumber breeding process.