Based on the bench-scale opposed multiburner (OMB) gasifier, a new combination of the optical sectioning tomography (OST) and two-color method has been proposed and applied to reconstruct the three-dimensional (3-D) temperature distribution of the gasifier by employing a single charge-coupled device (CCD) camera installed on the top of the gasifier. The reconstruction method is first applied in diesel gasification and the reconstructed results are validated by calibrated thermocouples and a side imaging system; thus the 3-D temperature distribution of coal-water slurry (CWS) gasification is reconstructed. The results show that the temperature distribution is more spatially homogeneous and the average temperature is higher with blurry contours of flame than that of diesel. The overall temperature of the gasifier rises with the increase of oxygen to carbon ratio, and the high temperature region which ranges from 1700 to 2200 K remains in the axis of the gasifier steadily and remains a safe distance from the refractory wall, which makes the temperature of the refractory wall below 1550 K and makes the participating medium maintain a stable condition for gasification.