Aiming at the situation of abnormal effectiveness of the certain type HEAT during experiment, analyzed the manifestation and the reason of the abnormal effectiveness of the HEAT. Based on operation theory of the HEAT, we contrasted the marks on the steel target after both normal effectiveness and abnormal effectiveness of its warhead, and carry out analysis of mechanism and reason. This analysis could provide basis for abnormal HEAT elimination and technology regulatory measures for abnormal problems, and improve the quality of LE products.