Power saving is one of the key issues in mobile ad-hoc networks (MANET), while previous researches in MAC layer are mostly focused on improving the channel utilization by adopting variable-range transmission power control. In this paper we focus on the power savings in the network layer, and propose a power adjusting algorithm (we term it PAA). In the presence of mobile host’s mobility, PAA is designed to conserve energy by adjusting the transmission power to maintain the route’s connectivity and restarting the route discovery periodically to find the new better route dynamically. After analyzing the operations of PAA, we find that the length of route discovery restarted period is a critical argument which will affect power saving, so we propose an optimizing model which finds the optimal value of this argument by analyzing the energy consumption of this algorithm. PAA can handle the mobility of MANET by adjusting the transmission power and in the meantime save energy by restarting route discovery periodically to balance the energy consumption on route discovery and packets delivering. It is suggested that PAA can be implemented in the dynamic source routing protocol (DSR). Simulation results are provided, which demonstrate DSR embedded with PAA saves nearly 40% energy compared to DSR without PAA in the presence of high mobility.