The lifetime of a wireless sensor network (WSN) directly lies in the power consumption of the network. Thus one of the important problems is how to design an effective algorithm to prolong the lifetime of the sensor network as much as possible. In this paper, a layer-based power control algorithm is proposed for rectangular field sensor network. In this scheme, the width of the layers and communication radius can be computed according to nodes energy consumption. Hence, the energy consumption of the networks can be balanced effectively. Simulation results show that the algorithm could effectively extend the lifetime of the networks.