The invention discloses an overflow-type heat exchanger of an urban sewage source heat pump system, relating to a heat exchanger of an urban sewage source heat pump system. The invention solves the problems that the traditional heat exchanging technology has complex process flow and large occupying area in order to realize anti-plugging. The overflow-type heat exchanger comprises a first medium channel connecting chamber, a second medium channel connecting chamber and a plurality of third medium channel connecting chambers, wherein two to four medium channels at the upmost end of a pipe shell assembly are communicated in parallel through the first medium flow connecting chamber to form a first medium channel group, and the first medium channel connecting chamber is close to a medium outlet; and two to four medium channels at the lowest end of the pipe shell assembly are communicated in parallel through the second medium channel connecting chamber to form a second medium channel group, the second medium channel connecting chamber is close to a medium machine inlet, and the plurality of third medium channel connecting chambers are used for serially connecting the second medium channel group, the first medium channel group and other medium channels together. The invention is suitable for the urban sewage source heat pump system.