Abstract: The gas-liquid two-phase flow behavior and mass transfer characteristics in microchannels are reviewed. The flow patterns in microchannels could be divided into bubbly flow，slug flow，annular flow and slug-annular flow，but no stratified flow，and the mass transfer efficiency increases by 2-3 orders of magnitude over that in conventional-sized devices. The formation，growth and coalescence of bubbles and their effect on gas-liquid two-phase flow in microchannels are also discussed. The progress of numerical simulation of gas-liquid two-phase flow in microchannels are introduced briefly. The research and application prospects of gas-liquid two-phase flow in microchannels are predicted from the aspects of experiment，theory and numerical simulation.