Sustainable Emergency Material Reserve Systems (SEMRSs) are complex frameworks comprising three types of reserves, namely, physical, capacity, and agreement reserves, and involve various stakeholders such as local governments and enterprises. However, multiple stockpiling methods have not been considered in investigations on the influencing factors and inter-factor relationships within an emergency material stockpiling system. In this study, we achieved consensus through a questionnaire, established an evaluation system encompassing various reserve methods and participating entities, and delineated the key factors affecting SEMRSs while analyzing their causal relationships using the decision-making trial and evaluation laboratory–based analytic network process. Results reveal that (1) local governments and participating enterprises play crucial roles in ensuring the sustainable supply of emergency provisions; (2) the capacity to guarantee emergency funds serves as a pivotal link among all key influencing factors, emergency funds should be augmented, and the utilization of contingency funds should be rationalized; and (3) the integration of physical, production capacity, and agreed stockpiling methods in the emergency reserve system requires enhancement, and the incorporation of capital reserves should be considered as part of the stockpiling strategy. These insights hold significant implications for refining emergency stockpiling practices and fostering the development of SEMRSs.