Abstract: The outstanding characteristics of sewage sludge are the high moisture content. The moisture of sewage sludge cake after mechanical dewatering is still as high as 80%. It is difficult to sewage sludge treatment both efficiently and economically, due to its high moisture content and bulkiness. However, decreasing the moisture content of sludge is the crux of the matter in harmlessness and bulkiness reduction, which is also the premise of resource utilization. Heating drying is one of the most effective methods of sludge deep dehydration, but the traditional hot air convection drying has many problems, such as low efficiency, high energy consumption and difficult tail gas treatment. Heat pump drying is a new technology of sludge low temperature drying, which has the advantages of low energy consumption, easy control of drying process and high safety performance. However, it is necessary to consider the size and stability of the sludge particles entering the dryer, coordinate the heat and mass transfer inside and outside the sludge particles, and deal with the impact of the dust and corrosive gas in the drying process on the heat pump heat exchanger.