Bubble formation mechanism and slug flow characteristics have been studied in a T-junction rectangular micro-channel under pulsating gas intake conditions. A high-speed camera is used to track the trajectory of gas-liquid interface by the Lagrangian method, while the numerical simulation is used to acquire the flow field distribution at different moments using the Euler method. The dynamic pressure, shear stress and pressure difference across the forming bubble at the T-junction increase with the pulsation frequency and liquid velocity. Under pulsating gas intake conditions, none of these three types of force can be neglected, indicating a transition regime between squeezing and dripping regime. The evolution of bubble length under pulsating conditions is similar to the general gas-liquid flow, but with a shorter value, while the liquid slug length is longer than the latter. The slug flow is transformed into wave flow when the pulsation energy inputted to the system reaches a critical value. The bubble velocity varies periodically over time with a main fluctuation frequency equal to that of pulsation. The present work proves that the technique of pulsating gas intake enables precise control the gas-liquid Taylor flow pattern, which would be useful for future application in gas-liquid reactions.