T-shaped tubes are widely used in the industry for the bifurcation of fluids. However, safety issues concerning the shock wave and spontaneous ignition resulting from the release of high-pressure hydrogen into T-shaped tubes are still challenging. That is because the flow direction of pressurized hydrogen can be different when we change the inlet of the T-shaped tube. In this paper, the effect of the flow directions in T-shaped tubes on the over-pressure, shockwave, and spontaneous ignition is studied. Results show that differences in evolution of upstream pressure are not obvious even if the flow direction is different. But the flow features both in the trunk and branch pipeline downstream of the bifurcation point are significantly different, manifested in the shock wave's velocity and the overpressure (shock-induced overpressure and maximum overpressure). The critical release pressure required for self-ignition is affected by the flow direction. When flow direction of the pressurized hydrogen can directly hit the wall in the T-shaped region, the critical release pressure is the lowest, even lower than that in the straight tube. However, the flame with another flow direction is unstable under the critical release pressure, which can sometimes induce the extinguishment. In addition, regardless of the different flow directions, the flame undergoes a reduction in intensity after the bifurcation and outside flames have similar evolutionary and morphological characteristics.