The pseudo range and the precision of pseudo range variability from ground-based pseudolite navigation system are very important to the navigation performance of evaluation system and the fusion of pseudo range information with the navigation information from other system. At present, the evaluation methods of pseudo range precision are basically aimed for satellite navigation system and they don't take full account of the characteristics of ground-based pseudolite navigation system. By constructing the precision observations of pseudo range and its variability and utilizing some bad positioning configurations produced by ground-based pseudolite navigation system, a precision evaluation method for pseudo range and its variability which can get accurate precision estimator even the exterior ballistic measuring system has low position-velocity precision and owns arm length was proposed. The simulation results indicate that the method can evaluate the precision of pseudo range and its variability effectively and has a strong applicability. 