Abstract: In order to solve the problems of reverse osmosis concentrated water to restrict the waste water zero emission realized from modern coal chemical indus trial park, the reverse osmosis concentrated water was retuned to the preparation of the coal water mixture. The bituminous coal and lignite coal were selected as the m ixed coal samples, the percentage adjustment of the reverse osmosis concentrated water was applied to verify the slurryability and to analyze the calcium ion concentra tion affected to the rheology of the coal water mixture. The experiment results showed that with the water quantity added to the reverse osmosis concentrated water incr eased, the mixture concentration would be continuously increased and the rheology would be worst and worst. In order to ensure the apparent viscosity would not be Ov er 1200 m Pa's when the shearing rate was 100 s(- 1) , the added percentage of the reverse osmosis concentrated water should not be over 50%.With the calcium ion concentration increased from0 to 1 867. 40 mg 1 L, the apparent viscosity of the coal water mixture would be improved from 1 041 m Pa.s to 1 468 m Pa.s. The above s howed that the calcium ion could neutralize the negative electric load on the surface of the coal particles and would not be favorable to reduce the viscosity, So the fluid ity of the coal water mixture became poor.