GNSS receiver could not be used in indoor environments. This paper proposes a novel pseudolite positioning approach utilizing carrier phase difference measurements, which can achieve sub-meter accuracy without the support of a base station, and without the need of synchronization between pseudolites. In addition, in the proposed approach, the integer ambiguity resolution is unnecessary as well. This research builds up system model for pseudolite positioning and proposes basic principle for this positioning method utilizing carrier phase difference measurements. First, two sets of carrier phase measurements output from a dual-antenna receiver are differentiated in order to cancel out the common errors. Then a non-linear least square adjustment method is used to solve spatial coordinates of center point of the dual-antenna iteratively. Simulation results and experiment outputs from a dual-antenna software receiver verified the feasibility of this approach. This pseudolite positioning approach can be regarded as an effective complement of existing indoor positioning techniques.