Geometric dilution of precision (GDOP) represents the geometric effect on the relationship between measurement error and positioning determination error. In the calculation of GDOP value, the maximum volume method does not guarantee the optimal selection of the four measurement units. The conventional method for calculating GDOP is to use matrix inversion to all subsets. In this paper, we employ GDOP using the matrix inversion method to select appropriate base stations (BSs) in cellular communication systems. The proposed BS selection criterion performs better than the random subsets of four or five BSs chosen from all seven BSs. The performances of MS location strongly depend on the relative position of the MS and BSs. Therefore, it is very important to select a subset with the most appropriate BSs rapidly and reasonably before positioning.