In order to assist making decision of determining the functionally significant items of the equipment, aiming at the shortcomings of the existing methods, the interval number multiple index decision problem is introduced. In combination with the priority of each attribute index, the traditional interval number TOPSIS method is improved. An interval number TOPSIS method with attribute priority is proposed to determine the functionally significant items of the equipment. The test results show that this method can guarantee the objectivity of the functionally significant items and reflect the degree of risk of different decision-making. At the same time, the method calculation is simple and the method is easy to implement computer program, and has strong application and popularization.