Condensed-mode operation of an ethylene polymerization fluidized-bed reactor is of great significance in academic and industrial circles. Based on the classical emulsion-bubble two-phase model, this article proposes an FBR model for condensed-mode operation by taking into consideration the addition of a condensed liquid and its evaporation. In this model, two different flow regimes, the gas-liquid-solid (G-L-S) and gas-solid (G-S) zones, are assumed to coexist in one FBR Moreover, the emulsion phase in the FBR is regarded as being in plug flow in the G-L-S zone and in well-mixed flow in the G-S zone, whereas the bubble phase is always treated as being in plug flow throughout the whole FBR Modeling of the temperatures of the emulsion and bubble phases allows the temperature profile of the ethylene polymerization FBR to be obtained. The simulation results show that the bed temperature rises sharply in the G-L-S zone above the gas distributor and then remains nearly constant in the G-S zone. Moreover, the G-L-S zone gradually expands upward with a corresponding increase in condensed liquid in the recycling stream. The simulated results compare fairly well with those from an industrial FBR unit. Based on the proposed model, the effects of bubble size on heat transfer and bed temperature profile were also studied.