Abstract: The research development of reheat crack of low-alloy steel used for pressure vessel is introduced from three aspects: affecting factors, formation mechanisms and measures for preventing the reheat crack. For the further study, it should be strengthened according to the following two aspects: one is the effect rule of interaction effect between different alloying elements on the reheat crack, and the other is comprehensively applying many mechanisms to explain the reheat cracking phenomena appearing in the engineering practice.