In order to objectively and fairly evaluate the trade efficiency level of countries along "YU-XIN-OU" and comprehensively grasp the various aspects and internal mechanism of the countries' trade efficiency, it is necessary to make a comprehensive evaluation of the national trade efficiency.This requires the establishment of a set of index system that both objectively and accurately reflect the various aspects of the national trade efficiency and take into account the internal structure of it. This also needs to use scientific and rational evaluation model to evaluate and analyze it.The evaluation index system of national trade efficiency involves all aspects of the indicators, so the indicators are complex and diverse. If the index number is too much, it will bring a lot of calculation and data processing difficulties to the evaluation,thus affecting the results of the evaluation. Therefore, it is necessary to select, optimize and deal with the evaluation indexes, and establish the index system for evaluating the efficiency of the national trade.This article based on the internal function mechanism of the efficiency of the national trade, starting from the two aspects of domestic and international trade, strive to explore the establishment of an evaluation index system of national trade efficiency and its mathematical model，which is rich in content, logical reasonable, broaden their horizon, with scientific and forward-looking.