In this paper，the detection and estimation of the fall point for reentry vehicle is studied. In the first，we introduce the concept of addmissible accuracy limit and then give the Bayesian posteori probability ratio odd testing method. For the systematic error of fall point，the Bayesian and constraint Bayesian estimation are discussed. The attention for using prior information is sufficiently mentioned so that the decision making of fall point can be carried out under the condition of small sample number.