The sewage pump is a type of un-logged pump, being applied mainly in the transportation of fluid, including suspending solid substances such as fibre, wastepaper, and grains. It is used extensively in environmental protection, civic works, irrigation works, and the disposal of sewage and industrial waste. To realize the un-logged capability of sewage pumps, the key importance lies in the model of impeller con. This paper briefly analyzes common models of impeller structures presently used in sewage pumps and their advantages and disadvantages, probing into the features of both enclosed-blade impeller and channel impeller and comparing their hydraulic design and their primary geometrical parameters. Experimental results show the following features of the channel pump: a steeper H-Q curve, a more planar P-Q curve, a higher peak value in the η-Q curve and a wider region with high performance. Addtionally, the channel impeller has the advantages of anti-twistability, un-logged, un-obstructed, transporting the high concentration fluid medium and running reliably. Therefore, it is a growing trend that the channel impeller substitutes the common enclosed-blade impeller, which is usually applied in the design of the sewage pump and is reference to popular practice.