In this paper,we have studied hot carrier injection(HCI) under alternant stress.Under different stress modes,different degradations are obtained from the experiment results.The different alternate stresses can reduce or enhance the HC effect,which mainly depends on the latter condition of the stress cycle.In the stress mode A(DC stress with electron injection),the degradation keeps increasing.In the stress modes B(DC stress and then stress with the smallest gate injection) and C(DC stress and then stress with hole injection under V g = 0 V and V d = 1.8 V),recovery appears in the second stress period.And in the stress mode D(DC stress and then stress with hole injection under V g = 1.8 V and V d = 1.8 V),as the traps filled in by holes can be smaller or greater than the generated interface states,the continued degradation or recovery in different stress periods can be obtained. In this paper, we have studied hot carrier injection (HCI) under alternant stress. Different stress modes, different degradations were obtained from the experiment results. The different alternate stresses can reduce or enhance the HC effect, which mainly depends on the behind condition of the stress cycle. In a stress cycle A (DC stress with electron injection), the loss keeps increasing. In the stress modes B (DC stress and then stress with the smallest gate injection) and C (DC stress and then stress with hole injection under V g = 0 V and V d = 1.8 V), recovery appears in the second stress period. End in the stress mode D (DC stress and then stress with hole injection under V g = 1.8 V and V d = 1.8 V ), as the traps filled in by holes can be smaller or greater than the generated interface states, the continued degradation or recovery in different stress periods can be obtained.