One of the most important applications for mobile commerce is location-based application and the core technology of location-based applications is the location determination technology. In this paper, we present a positioning method, called as cell-based positioning method and its positioning accuracy measure for the wireless networks with hexagon structure and mesh structure. In addition, the positioning accuracy is optimized by tuning the base stations? transmission power. In the optimal transmission power, an accuracy of within 9.1% (7.2%) cell area for hexagonal structure (mesh structure) can be achieved by cell-based positioning method. We believe that the results are useful to deploy wireless networks for location-based applications.