In order to reveal the propagation characteristics and hazards of a gas explosion in urban drainage pipeline, the dynamic evolution of a methane deflagration in a closed water-containing pipeline was numerically simulated based on Computational Fluid Dynamics (CFD). The interaction mechanism between water oscillation and flame development during the methane deflagration was such revealed. The results show that the presence of water accelerates the flame propagation in the forward accelerating stage. However, the water generally played a significant role in inhibiting the flame propagation because of its cooling and blocking effects. And the flame acceleration may be enhanced with the water present if a longer tube is employed. The shear force generated by the compression wave acting on the stagnant water surface provides the most primitive power for the movement of water, which creates ripples in the calm water. The obstacles and the reciprocating motion of the compression wave make the water ripple and evolve into lifting thin water columns. The shearing effect of high-speed gas flow evolves the water columns into discrete water droplets. This evolution process of the water body increases the contact area between water and flame, thus blocking the transfer of heat and the expansion wave, inhibiting the self-sustained flame propagation, leading to its gradual extinction. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.