As an energy-saving and environmentally friendly technology, the urban sewage source heat pump (USSHP) had been widely applied in the field of heating and air conditioning. Chinese researchers recently designed an urban sewage source heat pump system composed of a filth block device. a wastewater heat exchanger, a heat pump. and other assistant facilities, such as pumps, fans, and end user devices. The system was built in 2008, and has been in operation since then. We tested the parameters of the system oil the heating and cooling status from the wastewater source to the heat pump, including the temperature and flux of sewage, the inlet and outlet parameters of different facilities. and the performance of different facilities for a typical operation status. Based on the test results, the overall COP of the system in the heating and cooling mode was computed, and the energy efficiency level was analyzed Then a method was proposed to improve the system's performance. After the improvements, the characteristic Curves of the typical operation status were investigated. The results indicated that the heating COP is about 4.3, and the cooling COP is about 3.5 in the actual operating conditions These results could serve as a reference for designing or evaluating urban sewage Source heat pump systems. (C) 2009 Elsevier Ltd. All rights reserved.