On the basis of analyzing the mechanism of coal-water paste (CWP) slip flow, the similitude criterion, known as general Reynolds number Re-g which can characterize the state of non-Newtonian fluid flow in pipes, was put forward. The energy loss coefficient of CWP laminar flow has the same form as Newtonian fluid, i.e. lambda = 64/Re-g. Re-g holds good not only for the slip flow of non-Newtonian fluid, but also for slip-free flow as a steady-state laminar flow in pipes. The results obtained from experiments show that the energy loss coefficient of CWP laminar flow in pipes has the same form as Newtonian fluid. (C) 2002 Published by Elsevier Science Ltd.