Based on a flame image processing technique, the temperature distributions of flame sections in a bench-scale opposed multi-burner (OMB) gasifier is visualized. With the assumption of the gray radiation, a charge-coupled device camera installed on the top of the gasifier is used to capture the approximately monochromatic radiant images under the visible wavelengths. To reduce the errors, the camera is calibrated by a blackbody cavity. By using the two-color method, the radiant intensity captured by the camera is calculated from the pair of red/green with reference to the calibration data. Based on the assumption of rotational symmetry, the temperature distributions of flame sections are reconstructed by the Filtered back-projection method. The results show that the temperature distributions of flame sections are consistent with the flame structure. The flame temperature distribution at the burner plane ranges from 1700 to 2100 degrees C. The section is farther from the burner plane, the temperature is lower. The relative errors between the calculated temperatures and the measured temperatures by a B-type thermocouple are no greater than +/- 6.4%. The research results establish the foundation for understanding the flame internal structure and temperature distribution in the OMB gasifier. (C) 2008 Elsevier Ltd. All rights reserved.