Cycle-combined heat exchange process is a solution to improve heat exchange effect between two thermal mediums. Since limitation values of performance parameters in thermal systems can be obtained by constructing ideal thermal processes, for the purpose to study characteristics of cycle combined thermal process to guide practical design, concepts of reversible heat exchange process are presented in this paper. It is one theoretical simplification of isolated heat exchange system, which is comprised of exothermic medium, endothermic medium and combination of infinite sequential thermal cycles. In this research, the strict definitions of concepts of reversible heat exchange process are proposed and based on medium flow direction, and this reversible process is classified into six forms. With these basis, the thermodynamic analysis on each process is conducted and mathematical models are established with proper assumptions. Limitation analysis on the isolated heat exchange process is conducted and results shows that reversible heat exchange process is the limitation case of the isolated heat exchange process, in which the upper (lower) bound value of exothermic (endothermic) medium outlet temperature and available maximum amount of exchanged heat will exist theoretically. In addition, the practical application of limitation analysis of isolated heat exchange process is also provided.