Mobile location estimation has attracted a significant amount of attention in recent years. The network-based location estimation schemes have been widely adopted based on the radio signals between the mobile device and the base stations. The two-step Least Square (LS) method has been studied in related research to provide efficient location estimation of the mobile devices. However, the algorithm results in inaccurate location estimation with the existence of the Non-Line-Of-Sight (NLOS) errors. A Geometry-constrained Location Estimation (GLE) algorithm is proposed in this paper with the consideration of different geometric layouts between the mobile device and its associated base stations. In order to enhance the precision of the location estimate, the GLE scheme is designed to incorporate the geometric constraints within the formulation of the two-step LS method. The proposed GLE scheme can both preserve the computational efficiency from the two-step LS algorithm and obtain precise location estimation under NLOS environments. Numerical results demonstrate that the proposed GLE algorithm can achieve better accuracy, comparing with other existing schemes, in mobile location estimation.