Abstract: A new localization algorithm was proposed for improving precision of range-free localization. The algorithm is based on a partitioned circle whose radius was equal to the node communication range. A partitioned circle can separate the anchor nodes around the target node into two parts. A function was used to calculate the offset between such partitioning results and the real one-hop and two-hop anchor node sets. By searching a certain area, the optimal partitioned circle can be selected. The center of the optimal partitioned circle is regarded as the position of the target node. Simulation results show that the new algorithm significantly increased localization accuracy, especially for nodes at the edge of the networks.