Abstract: The novel grid-based distributed localization algorithm for wireless sensor networks is introduced，which is called Intersection-Grid-Sector（IGS） for range-free localization.The IGS can obtain intersection grid coordinates through grid unit of one hop area intersection of every anchor around unknown node，which is divided into grid unit based on 10% of anchor node radius.Then，IGS calculates the Center Of Gravity（COG） of the intersection grid coordinates in which a node resides to determine its estimated position.Simulation shows that IGS algorithm estimation error compared with Bounding Box is significantly improved and compared with classical Centroid ascends about 20%.