Indoor GPS measurement network is a space coordinate measuring system, which is composed of more than one transmitter. The number and location of the transmitter determine the measurement range and accuracy of the measurement network. Therefore, how to correctly evaluate the measurement network is a key issue. By analyzing the error model of a measuring system, which is composed of two transmitters, we acquired the main cause of the measurement uncertainty. Through MATLAB simulation, we are able to get the effective measurement conditions, in order to meet specific requirement of measurement uncertainty. Meanwhile, total uncertainty of the measurement network, which is composed of measurement uncertainty, location uncertainty, receiver uncertainty and other uncertainties, is analyzed. We proposed the evaluation method based on the reference length, and at the same time, optimized the position of the reference position, posture and length, in order to meet the evaluation requirements of the entire measurement space. Finally, we simulated the measurement network for aircraft assembly in measurement space of 20m×20m×5m, and the measurement network for car assembly in measurement space of 5m×5m×2m. We evaluated the measurement network according to the above principles and estimated the uncertainty of the measurement network trough measurement bias of reference length at different locations.