The effect of particle size distribution of petroleum coke on the properties of petroleum coke-oil slurry (PCOS) from four Chinese petroleum coke samples, such as apparent viscosity, rheological behavior, static stability, were systematically investigated. The size and morphology of petroleum coke particle with different grinding time and the corresponding stabilizing mechanisms were analyzed by SEM and zeta potential measurements. Experiments proved the petroleum coke grinding time of 60 min is suitable for the particle distribution and stability of PCOS. Besides, the effect of the sample type and loading of petroleum coke on the properties of PCOS was studied. The factors governing the apparent viscosity and stability of slurries have been discussed. The experimental results showed that the properties of PCOS could be effectively improved, and a suitable PCOS with low viscosity and good stability could be prepared through controlling the particle size distribution and petroleum coke loading. (C) 2011 Elsevier Ltd. All rights reserved.