Abstract: The development of DFFR stays in the phase of conceptual design, which leads to the main discussion of this work that is to quantitatively evaluate the feasibility of this reactor type and the effects of those parameters on the reactor physical behavior. The evaluation includes two parts: the criticality calculation based on the Monte Carlo theory and the thermal-hydraulic calculation based on the heat transfer theory. The result shows that the DFFR can achieve the criticality with expected operational parameters and the feasibility of this reactor is therefore preliminarily proven.