Herein we experimentally investigated the influence of ethanol on condensation heat transfer of gravity loop thermosyphon in presence of massive non-condensable gas. Investigated results revealed that addition of 0.5%?1% mass fraction of ethanol formed Marangoni effect on the surface of condensate film, promoted local condensation heat transfer, and increased 9% local heat flux of the inlet section of the condenser. When the ethanol content was greater than or equal to 1.5%, ethanol cannot fully condense to form the new non-condensable gas, the pressure of the system and temperature of evaporator could be increased, and the higher ethanol content, the higher system pressure, the system pressure of 5% condition was 64% more than pure vapor condition.