Abstract: Distribution transformer is one of the key equipment in the power system. Its quality is directly related to the continuous and stable operation of the power system. At present, the the power transformer manufacturing industry is overcapacity. The quality of power transformers is different strictly. It has great significance to evaluate the power transformer suppliers with an objective quantitative method, which contributes to purchase high-quality equipment and ensure the safe and economic operation of the power grid. There are many researches on the method of supplier evaluation, which mainly focus on the research of evaluation index or index weight. Because of the weak data base and lack of large data support, there are many subjective factors in the process of determining the evaluation process. Most of the evaluation targets provide product quality, service, price and so on. Those methods do not consider the products of the evaluated suppliers. It cannot reflect the overall production level of the suppliers. State Grid Corporation of China (SGCC) has established the supplier database, including the supplier basic information, financial situation, report certificate, product performance, R&D design ability, production and manufacturing capacity, test testing ability, raw material and component management, after-sales service, capacity situation and so on. There are more than 55 thousand suppliers in the database. In the database, there are 600 suppliers can produce distribution transformer, which are verified by SGCC. The high quality database enhances solid foundation for supplier evaluation. The method of distribution transformer supplier evaluation based on entropy weight method is proposed. According to the current status of power enterprise supplier management, dig into the database information. The information includes qualification, social credit, and the life cycle quality and service information of its products in production, installation, commissioning, operation and maintenance, etc. The evaluation index is divided into three levels. The first level includes 4 indexes. The second level includes 14 indexes. The third level includes 47 indexes. The evaluation indexes are comprehensive, objective and quantifiable, and the evaluation method is also objective, which avoiding subjective impact and realizing the objective quantitative evaluation of suppliers. Finally, the method is applied to distribution transformer suppliers for example analysis, which verifies the practicability of the evaluation method.