In most conditions, the excess heat of exhaust water discharged from household or publicbathing-rooms is mostly not utilized, which causes a lot heat loss for its higher temperature. For thisreason, it is suggested that a heat pump that uses the exhaust water as a low-temperature heat sourceshould be used to reclaim its excess heat to produce sanitary hot water for the public bathing-rooms. Inthis way, we call the above-mentioned heat pump as bathing room heat pump water heater. In thispaper we presents the components and flow diagram of the heat pump water heater with heat recoveryapplied in public bathing-room, analyzes its thermal characteristics from thermodynamical principles,and calculates its limit heating coefficient under different typical working-conditions. The computationalresult shows that in theory, the maximum value of its is up to 12.9 under a typical operating condition.