Wireless sensor networks (WSNs) are more and more widely used in many different scenarios. The localization information is an important criterion for the capability of WSNs. Centroid algorithm is a classical range-free localization algorithm. After receiving the anchor nodes, a node estimates its location using the centroid formula. But the set of the asymmetrical anchor nodes distributed around the unknown node may incur large error, and will jeopardize the localization precision. In order to solve the problem, we propose a Centroid algorithm with selective anchor node localization algorithm (SA-Centroid) for WSNs in this paper. The triangle centroid and polygon centroid were used and the method of selecting nearest anchor node was adopted. The experiment results illustrate that our algorithm is valid and effective.