Abstract: Aiming at the ambiguity, uncertainty, and grey characteristics in the service quality evaluation process of medical caring and nursing combined institutions for the aged, a service quality evaluation method is proposed through the interval-valued Pythagorean fuzzy set (IVPFS)-decision-making trial and evaluation laboratory (DEMATEL) and a two-stage decision model with grey synthetic measures. Based on the SPO model(structure-process-outcome), a service quality evaluation index system for medical caring and nursing combined institutions for the aged is established. Further, a new method is proposed to determine the index weight through combination of IVPFS and DEMATEL, followed by the two-stage decision model with grey synthetic measures is used to assess the service quality of medical caring and nursing combined institutions for the aged. Taking medical caring and nursing combined institutions for the aged in four typical cities of Jiangsu Province as target examples, the effectiveness of the proposed model is verified by comparing with other method. The results show that the proposed methodology can effectively evaluate the service quality of medical caring and nursing combined institutions for the aged.