As the key element in power system

the safe operating of transformer is close correlative with the safety of the power system.So it is important to determine accurately the operation status of running transformer.At present

mostly research of integrated condition assessment of transformer is only present the evaluation grade of a single transformer condition

and not achieve rank many transformers according to their condition.This paper studied of TOPSIS in multiple attribute decision making

improved normalization formulas of income-type index and cost-type index

gave the definition of positive ideal solution and negative ideal solution

making it suitable for Integrated condition assessment and ranking of power transformer.It also gave the integrated condition assessment model of power transformer based on TOPSIS

making power enterprise to grasp many transformer conditions as a whole and to decide to examine transformers.Analysis of real example illustrates that our method is rational and effective.