Petroleum coke residual oil slurry (POS) is a new kind of substitute fuel that is developed for burning oil boilers of power plant. It is a mixture of pulverized petroleum coke and residual oil. It can not only make good use of petroleum coke, but also save fuel oil in quality. The experimental study on combustion character of POS is done through a series of experiments on 0.4MW test facility in this paper. The experimental results show that POS with high concentration of 40% pulverized petroleum coke can be prepared, heated, transported and burned and the combustion efficiency is high. The parameters such as POS concentration, POS heating temperature, fuel load and oxygen content have high influences on combustion efficiency. In addition, discharge behaviors of pollutants such as NOx, SO2, and CO are also discussed when the POS is burned in the chamber.