In view of the technical problems of difficult-to-settle slime water purification and treatment in wet coal preparation process，such as difficult settling，low treatment efficiency and high cost，this paper discussed the research and application status of new technologies of slime reduction technology，agent system optimization，water quality regulation，electromagnetic field enhancement，microwave treatment，microbial treatment，high efficiency concentration and pressure filtration from the aspects of slime source control，slime water treatment method and slime water terminal treatment equipment，combined with the production practice of difficult settling slime water treatment in Shendong mining area. The problems existing in the industrial application of the whole process treatment technology of difficult-to-settle coal slurry water were analyzed，and the development trend of the technology was prospected. The slime reduction technology is the source of the treatment of difficult-to-settle slime water. The amount of slime entering the slime water system could be reduced by efficient dry screening of feeds using flip-flop screen. For the established and mature coal preparation plants，the yield of secondary slime often could be reduced with measures of the optimization of process flow，the reduction to screen gap of the screen basket，the regulation of operating process parameters. In order to reduce the mixing of fine gangue，the methods for using heavy-medium cyclones with pressureless feed，reducing screen gap of the gangue screen for medium-removing，separately treating unqualified media of gangue，separately settling and treating water of high-frequency sieving under the condition of meeting the production requirements. It could contribute to control the water volume of the slime water system and prevent mixing of coarse-grained materials through strengthening the production organization and water management. The treatment technology of difficult-to-settle slime water is the core of slime water treatment. Inorganic calcium salts and other high-priced metal cations can be added to the slime water to adjust the water quality of the slime water and promote the coalescence of coal slime particles. The yield of slime is effectively reduced by deep classification using electromagnetic vibrating high-frequency screens. The effects of flocculation and sedimentation could be strengthened by improvement of the concentration，filter press process and equipment，using of the electric field，magnetic field，microwave field treatment and microbial flocculation agent. Besides，the side effects of chemical agents on the environment could be reduced. The slime water terminal treatment equipment is the foothold and starting point of the difficult-to-settle slime water treatment. At present，it is mainly developing in the direction of large-scale，localized，high-efficiency，and intelligent.