Reasonable determination of index weight is of great importance to get an objective and reasonable evaluation result of water saving and improvement evaluation in irrigation district.In order to obtain the objective and reasonable index weight,two kinds of combination weighting method with different principles are applied to index weight calculation and the calculated result are applied to benefit evaluation of water saving and improvement in irrigation district.It is found that the two kinds of index weight vector sequences are the same. The sequences of the two kinds of evaluation result for four irrigation districts based on the two kinds of weight are the same though the evaluation values are different.Finally,the causes of the result and the application condition of the two kinds of combination weighting method are analyzed.