In order to objectively and systematically evaluate the technical transformation and upgrading plans of secondary equipment in substations, a differential technical transformation model for substation is constructed to realize the differentiation and precision of technical transformation. Firstly, by analyzing the historical information record of the secondary equipment and related norms and standards, combined with the actual operation of the substation, the evaluation index system of the transformation scheme is constructed. Secondly, the evaluation rules are improved, and the calculation models and quantitative methods of each indicator are given. Thirdly, the triangular fuzzy number in analytic hierarchy process is used to solve the multi-attribute decision making model. Finally, an actual case of differential technology transformation is used to verify the validity of the improved model, and the evaluation results with better discrimination are obtained.