Provided is a state evaluation method of an overhead transmission line. The method adopts a multi-layer fuzzy synthetic evaluation model. A two-stage fuzzy synthetic evaluation rating model is adopted for the overhead transmission line. The concrete evaluation process comprises following steps: firstly, evaluating the stage of a line unit, deducing marks for defects based on weight of defects and severity and obtaining the state of the line unit by the maximum value of all defection subtraction scores and summing value summing value; then, evaluating the stage of poles and towers with states affected by four factors including the line unit, operation years, environmental regions and weather, and finally obtaining the overall state of the line by synthesizing all states of poles and towers. The subtraction of the line unit is obtained by weight of the unit and the state. The subtraction of the operation years is obtained by operation years. The subtractions of environmental regions are obtained by weight and risk degrees. According to the total subtractions and maximum subtraction scores for four factors, states of poles and towers can be obtained.