The concept of cooperative group localization (CGL) scheme, based on the measurements of time of arrival (TOA), is to solve the ill-conditioned cellular localization. In the light of CGL’s traditional searching and positioning algorithm, the paper proposes an improved geometric factor-based searching and positioning algorithm for CGL. In the suggested algorithm, the mobile terminals (MTs) which communicate with a new base station are supposed to be selected preferentially when choosing the next one for positioning. The geometric relationship between MT and its reference terminals (other MTs or base stations) is first put forward as an essential reference index to choose the successor positioning MT. The relationship between the geometric factor and positioning accuracy is completely proved in the theory in this paper. The simulation results indicate that the improved algorithm enjoys higher positioning accuracy than the traditional algorithm at a lower complexity.