Experimental visualizations and numerical simulations were carried out to investigate the bubble generation mechanisms in a microchannel with double flow junctions. Two kinds of flow patterns could be observed from the experiments and simulations: slug-bubble flow and split flow. When 0.00554 < Ca-2 < 0.025 and 0.25 < Q(G)/Q(L) < 6, slug-bubble flow can be observed. When Ca-2 < 0.00554 and 6 <= Q(G)/Q(L) <= 8, split flow will occur. Bubble length and velocities were also analyzed experimentally and theoretically. The relationship between bubble length, Ca and flow rate ratio Q(G)/Q(L) was obtained by regression, and the correlation could predict the data within an RMS error of 20%. Bubble velocity data correlated with the drift flux model showed that the distribution parameter of the two flow junctions C-01 and C-02 had values of 1.0654 and 1.1123, respectively.