Abstract: The lifetime of a wireless sensor network (WSN) directly lies in the power consumption of the network. Thus one of the challenging problems is how to place the sensor nodes efficiently to prolong the lifetime of the sensor network as long as possible. First analyzed in this paper is the optimal placement for single source under the linear network model. Based on the analyses, an energy-efficient deployment algorithm under the linear network model is designed, then it is extended to adapt to the planar network model. Based on the above work, a novel vector-based placement algorithm is proposed. In this algorithm, by calculating the positions of the relay nodes to gather the data from the sources, the energy-efficient placement in the whole wireless sensor network is obtained, which contains fixed sensing nodes and given number of relay nodes. The results of simulation experiment illustrate that the network deployed by the algorithm can save about 50% energy of that deployed by regular algorithm when the ratio of source and relay number is 1∶2. Now this algorithm is used in the fire monitoring system implemented in the laboratory. In the practical application systems, the numbers of nodes are often limited because of the cost, so this algorithm is of significant importance to construct low cost application system of wireless sensor networks.