Droplet generation involving high inertial gas flow in a T-junction microchannel was experimentally and numerically studied in this work. The effect of high inertial flow on the water droplet generation was investigated based on the obtained results. At various gas Reynold (Re) numbers and liquid Capillary (Ca) numbers, the unique flow regime mapping including squeezing, dripping and jetting was observed. It was found that stable aqueous droplets are generated in the squeezing and dripping flow regimes. Visualization experiment shows that the morphology of droplets generated in the water-gas system is different from that in the traditional water-oil system. As the Re number increases or the Ca number decreases, the droplet length decreases. Increasing both Re number and Ca number can increase the detachment frequency. Based on the 3D VOF simulations, the droplet attachment to one of the channel wall during the pinch-off period and the rebound of liquid phase after droplet detachment was observed. Droplet size, detachment time and droplet generation frequency were then analyzed for the droplet generation. The dominant detachment mechanism during the whole droplet generation process was also discussed in this work.