Improving efficiency is an enduring effort for all refrigeration cycles. Real gases cause "intrinsic" heat losses in the regenerator and degrade the coefficient of performance (COP) of the regenerator of the refrigeration cycle. Previous experimental and numerical studies found that the COP of the regenerative refrigerator can be improved by imposing a direct-current (DC) flow, and the liquefaction rate can be improved by several times when the gas is precooled by the regenerator that works down to the temperatures close to or below the critical point However, the working mechanism of such improvements has not been fully explored. In this paper, the working mechanism of imposing a DC flow on the regenerator working with a real gas is revealed based on thermodynamic analyses. The theoretical value of the DC flow and its influence on the COP of the regenerator are analyzed. The results show that the COP of the regenerator can be improved by over 10 times with a DC flow. An even higher relative Carnot COP of around 80% is possible to obtain in some specific temperature ranges. The enthalpy loss and the entropy loss of this approach has been estimated. This approach provides a potential way to improve the refrigeration COP and the liquefaction rate significantly. Measured liquefaction results found in the relevant literature have been analyzed to demonstrate the effectiveness of this approach.