Recent advancement in wireless sensor networks has attracted growing research interest. In this paper, we propose a new routing mechanism Power Efficient Routing based on Sensor Nodes Density (PERD). We use a metric, the nodes density, to help our routing mechanism to select a power conservation route. The PERD can maximize the lifetime of the sensor network by making full use of power available nodes and keeping energy consumed evenly among sensor network with different node density. We use the ns-2 simulator and employ the dynamic source routing (DSR) protocol to evaluate the performance of our routing mechanism and prior proposals for power-aware routing. The simulation result shows that PERD achieves a better performance than the prior mechanisms.