The effects of temperature and pH on rheological characteristics of coalwater slurry (CWS) were investigated. With regard to effect of temperature, the experiments were carried out using a thermal cup at different temperatures in the range from 100 to 200 oF (37.8 to 93.3oC). The studied pH range of slurry was from pH 2 to pH 12. The apparent viscosity and non-Newtonian properties based on power-law model were investigated using a Chandler Engineering viscometer Model 3500LS+. It was found that the apparent viscosity and degree of pseudoplasticity sharply decrease with increasing slurry temperature. At temperatures greater than 180 oF (82oC) the coal slurry showed a Newtonian fluid behavior. The apparent viscosity increased with pH increase over all studied pH range. On other hand, the degree of pseudoplasticity sharply decreased with increasing pH to pH 6 and then increased. At pH equals 6 the slurry exhibited Newtonian fluid behavior. During transportation of coal water slurry, it was observed that the apparent viscosity increases with increasing number of pumping cycles. This was attributed to changes in particle size distribution as a result of particle degradation which, in turn, increase pressure drop along the pipeline. Hence, taking into account the effect of particle degradation in design of pipeline transportation of slurries is recommended.