The mine integrated energy system (MIES) is an important approach for supporting the green development of coal mines. Conducting a reasonable and effective evaluation of its operation benefits is an necessary prerequisite for promoting its development. However, evaluating the operation benefits of MIES requires not only consideration of the strong coupling between energy and coal flows, but also addressing the influence of operational uncertainties on the accuracy of the evaluation. To address these challenges, a MIES operation benefit evaluation framework is proposed based on the optimal clustering coefficient-based improved extension grey cloud (OCC-IEGC) model. First, considering the ecological characteristics of MIES, an evaluation index system is established based on the driving-pressure-state- impact-response (DPSIR) model, and the cloud-weighted selection method is applied to obtain an optimal rational combination weights. Second, the MIES operation benefit evaluation model based on the extensive grey cloud theory is constructed to mitigate the influence of system operational uncertainty, subjectivity and ambiguity during the evaluation process, while the optimal clustering coefficients are used to further improve the reliability of the evaluation results. Finally, the effectiveness of the proposed index system and evaluation model is verified through case studies.