Node self-positioning is a fundamental and crucial issue for sensor network operation, management and applications. In this paper, an efficient location method is proposed based on received signal strength information (RSSI). We first utilize the known-location nodes (anchor nodes) to locate the unknown-location nodes in a single-hop range, and the estimated nodes are regarded as new anchor nodes in the following position estimation. Similar process is carried out for the rest of the unknown-location nodes based on more anchor nodes. In order to overcome the diffusion effect of the accumulative error introduced by new anchor nodes, Taylor-series expansion method is applied to optimize the estimated values. It is shown the method mentioned in the paper enhances positioning accuracy of self-localization and reduces the dependency on priori knowledge of node coordinates in wireless sensor networks (WSNs).