Abstract: Due to the limited power supply, sensors have to switch between sleeping mode and awake mode at a low duty cycle to extend the network life-time. Therefore, when localizing a mobile node, it is possible that a seed node is passed by the mobile node during its sleeping mode, so that the mobile node cannot collect enough seed information and fails to be localized consequently. In this paper, a dynamic sleep scheduling mechanism, namely P-SWIM is proposed. In P-SWIM, each seed is proactively notified if a mobile node is moving toward it, so that only these seeds should remain active in full duty when the mobile node passes by them, while the other seeds can still stay in the low duty cycle mode. P-SWIM can ensure enough seed connectivity around the mobile node, which is necessary for successful mobile localization. Simulation results indicate that localization algorithms based on P-SWIM can achieve better localization performance than those based on the other two sleep scheduling mechanisms, RIS and GAF. Moreover, P-SWIM causes least running overhead to the network overall power consumption among the three mechanisms, at most 47.6% and 60.2% less than RIS and GAF.