In order to improve the reliability of rock mass quality evaluation in deep well mines and overcome the controversial drawbacks of indicator weight assignment in traditional evaluation models, five influencing factors were selected to construct a rock mass quality evaluation system. With the help of moment estimation theory, a reasonable descending sequence of indicator weights was obtained. Partial order sets were introduced into rock mass quality grading, and a comprehensive evaluation model for underground mine rock mass quality based on moment estimation theory partial order sets was proposed. Using 12 typical rock samples as sample data, the model was tested and compared with the results of matter element extension, uncertain measurement evaluation, and actual state. Finally, the model was applied to the quality assessment of a copper iron ore rock mass in Anhui Province. Based on the judgment results, a support scheme suitable for the rock mass stability classification was selected. The results show that the rock mass quality assessment based on moment estimation theory partial order set is consistent with the field investigation, and the optimized support scheme can effectively control the deformation of the roadway, verifying the feasibility of the model in rock mass quality assessment.