Under the circumstance that true values of measuring points are unknown， how to evaluate result of state estimation is the first and foremost problem to be resolved. This is also a difficult task in state estimation research. The reason causes the difficulty is analyzed， and the concept of normal rate of measuring point based on the theory of uncertainty of measurement is introduced. It is proven that the estimation result with higher normal rate is more rational， and the indices of judging the rational level of state estimation result are proposed. Moreover， a study on the relationship between normal rate and qualification rate which is used in practice is given. Detailed discussion is also given on the evaluation indices of state estimation result under the circumstance where true values of measuring points are known.