Abstract: Currently, the reactivation processes originating at the negative leader end remain poorly understood. To fill this gap, this study improves a self-sustained charge neutrality lightning model to successfully simulate reactivation along negative leader channels under a classic tripole thunderstorm charge structure and to analyze their discharge characteristics. The results show two types of reactivation at the negative leader end: spontaneous initiation and triggered initiation. Spontaneous initiation exhibits a cumulative evolution of the electric field and is associated with the outward extension of the negative leader channel, which transports charges of opposite polarity to cutoff points. This type of reactivation only marginally enhances the electric field at the active negative leader tip and has little influence on subsequent branch development. In contrast, triggered initiation is characterized by an abrupt increase in the electric field and is induced by reactivation at the positive leader end. It can recur at the negative leader end until the electrostatic energy transferred from the positive leader end is fully dissipated. Overall, reactivation at the negative leader end is weaker than at the positive leader end in terms of initiation frequency, discharge intensity, and impact on the leader channel. Moreover, the electric field strength within the corresponding discharge channel is typically only slightly above the initiation threshold, preventing sustained breakdown in poorly conductive channels. This study improves the capability of numerical models to simulate fine-scale lightning discharge processes and provides insight into the mechanisms underlying the marked differences between positive- and negative-end reactivation.