The longitudinal and cross-sectional temperature distributions are measured in reduced-scale tunnel fire experiments with different fire power conditions. Field tests are carried out in a utility tunnel with pool fires. The experiments studied the ceiling temperature along the tunnel centerline, the vertical temperature below the ceiling and the temperature in the direction of radian in the same section with the fire source. The results from the burning experiments are analyzed. The longitudinal temperature distribution along the tunnel can be fairly well fitted by exponential equations. And the thermal radiation of the smoke layer has a significant effect on the temperature below the ceiling. In addition, in the direction of tunnel radian, the temperature growth rate of the region above 45° are obviously faster and the temperature is higher. Therefore, to shorten the response time of the detector to the fire, it is desirable to place the heat and smoke detectors at the top of the utility tunnel.