The location of sensor nodes in wireless sensor networks plays an important role in most applications. In this paper, we address the anchor selection scheme by characterizing some sufficient conditions such that we can offer technical convenience for improving the localization accuracy. Based on the location estimates error analysis of the concentric beacon localization algorithm, 2 or 3 anchors selected by some optimization schemes are used for node localization. The coordinates can be computed by the intersection points of relative energy rings. Using the approximated center of intersections of the rings, the location estimates can be derived based on the centroid localization algorithm. Simulation results show that our proposed scheme achieves significantly better performance than conventional range-free algorithm, such as Centroid algorithm and concentric anchor beacon localization algorithm, in terms of localization precision and stability.