There is enormous recyclable thermalenergy in public baths bath wastewater. In this paper， the energy saving effect of different heat recovery systems had been compared ， a heat recovery systems and some practical engineering problems are proposed，in which the sewage source heat pump works as the main equipment. Meanwhile as an example the paper made an economic analysis of the project，Proved that the operating costs could be substantially reduced by using the heat recovery systems and be worth to be promoted.