For missile flight test, telemetering data and exterior ballistic measuring data are the basis of precision and reliability analysis. Usually, we assume that exterior ballistic measuring error has normal distribution with zero mean. But during the real measuring, it is possible for exterior ballistic measuring parameters to cause system error. It has bad influence on the information obtained from flight trajectory and fall point. With the given model hypothesis, the estimation of exterior ballistic measuring system error is obtained in this paper. Futher more，some simulating results and their preliminary analysis are given.