Based on the experimental analyses, the slip phenomenon of coal-water paste (CWP) flowing in pipes is investigated by tube flow test in different tubes. The origination mechanism and flowing regulation of slip phenomenon in pipes are analyzed and a method of determining the real theological models of CWP by correcting the influence of slip flow phenomenon is put forward. All kinds of CWPs behave as the properties of non-Newtonian Herschel-Bulkley fluids in the experimental range. At a certain particle size distribution the apparent viscosity of CWP increases with the increase of solid concentration. Fluidity of coal-water paste increases with increase of desulphurization additives under same concentration and particle size distribution. The optimum mass ratio of coarse coal powders to the fines in CAT for PFBC is determined. (c) 2004 Elsevier B.V. All rights reserved.