The invention relates to a medium heat exchanging unit, and relates to the technical field of energy saving and environmental protection equipment. The medium heat exchanging unit is characterized inthat a lower bottom plate of a housing is fixed to the bottom part of an outer barrel body, wherein the lower bottom plate of the housing is mounted on a base; an upper bottom plate of the housing isfixed to the upper end of the outer barrel body; a lower inner tank barrel body is arranged in the outer barrel body, and an inner tank tube plate is mounted on the lower inner tank pipe body; an upper inner tank barrel body is arranged at the upper part of the lower inner tank barrel body; an inner tank top plate is fixed to the upper inner tank barrel body; the upper inner tank barrel body is connected to the lower inner tank barrel body through a plurality of connecting pipes; an irregular tube seat of an electric heating tube is mounted between the upper bottom plate of the housing and theinner tank top plate; the electric heating tube is inserted into the irregular tube seat of the electric heating tube and extends into the lower inner tank barrel body; an expansion groove is connected to the inner tank top plate; an oil filling port and a pressure releasing valve are arranged on the expansion groove; and the lower bottom plate of the housing is connected to the inner tank bottomplate through a stretching supporting round steel. According to the medium heat exchanging unit, water and electricity are separated, so that the service lie of a heater is prolonged; the heat efficiency is high; the water storing capacity is high; and blockage is greatly avoided.