The generation of gas-liquid-liquid three-phase microflows in a cross-junction microchannel device is experimentally analyzed. Three gas-phase and eight water-phase flow manners at the cross junction are described with oil phase as continuous phase. Comparing with the gas-liquid and liquid-liquid two-phase microflows, similar flow behaviors of dispersed phases exist in the three-phase processes but new capillary numbers as well as the phase ratio of dispersed phases need to be introduced in the flow maps to distinguish the complicated three-phase flow modes. Although the three-phase flows are mercurial at the channel junction, only six flow patterns are observed in the downstream microchannel. According to the experimental results, the effects of bubble/droplet generation manners on their size distributions are indicated. The generation mechanisms of bubbles and droplets are analyzed and correlated equations are established for their average volumes.