During the assessment period of gas insulation state for GIS equipment

different weight definition and membership function selection method will lead to different assessment results

thereby affecting the accuracy of assessment result.For avoiding the influence of subjective factors

in this paper

the weights of each index is adjusted by introducing balance function on the basis of defining weights by the use of entropy method and in accordance with the variable weight theory.In addition

the combination of trapezium

Γshape and k parabola are used to define the membership function of each index so to avoid evaluation error due to single membership function.Finally

the comprehensive diagnosis model is used to define the gas insulation condition for GIS equipment and the evaluation result of the constant weights and single membership is compared.It is shown by the actual example analysis that this method can assess the insulation state of GIS equipment accurately and effectively.