Abstract: This paper points out the theoretic pitfall caused by evaluating the rightness of integer ambiguity solution based on the three-step approach of the traditional hypothesis test theory, and introduces the concept of the pull-in region for ambiguity and the definition of the admissible integer estimation. On the basis of the original definition for the admissible integer estimation, a new severer definition is given. On the basis of this new definition of the admissible integer estimation, the concept of ambiguity success rate is discussed and the corresponding formulas are deduced.