In order to solve the problem of fuzzy standard to assess aircraft supervision, combined with the actual implementation of supervision, a customer inspection items assessment system was introduced. An improved matter-element extension model was used to build the assessment model of supervision work, in order to carry out an accurate quantitative assessment to supervision. In this model, closeness degree was used instead of correlation degree, and each index was quantified to improved the accuracy of assessment. Through the practical example, the result is consistent with the operator’s feedback, which verifies the feasibility of the method. Through the accurate quantitative assessment of the supervision work, it provides the reference for operator to carry out supervision work, provides support for the following aircraft delivery work, and provides guidance for manufacturer to improve the quality of aircraft.