The explosion propagation characteristics in parallel pipes have been studied for the first time in two different types of pipe. It was found that flame speed and overpressure in two branches of equal length were close when the ignition was at the pipe head. The explosion violence was strengthened after the flame and blast wave were superimposed. When the ignition was acted in the corner of one branch, the peak overpressure near the meeting point was higher than that at the two adjacent points, while the flame speed showed a downtrend. When the parallel pipe was not full of gas, the peak overpressure in the two branches followed similar trends and showed an obvious downtrend. However, when the blast wave reached the meeting point, the peak overpressure also showed an obvious upward trend until the end of the pipe. The flame accelerated in the two different branches of unequal length, but it slowed down when traveling to the meeting point, and the peak overpressure evolution was contrary to the flame speed. The results suggested that the violence of the underground gas explosion near the meeting point was more serious, such that the equipment and people in this area should be paid more attention. (C) 2011 Elsevier Ltd. All rights reserved.