Abstract: A self-made transparent T-type bifurcation pipe was used. Ignition by the branch and test the change of photoelectric signal, ion current, temperature signal and overpressure signal during the propagation process of gas explosion flame front in the branching pipe that is completely closed at two ends and weakly closed at one end. The results show: The gas explosion flame in the T-tube is distributed to three ports, showing three typical states of layered flame, oscillating flame and deflagration flame. During the propagation of the flame to the completely closed branch pipe and the right end of the straight pipe, the velocity and ion current intensity are small(maximum 1.32m/s, 0.024μA), and the propagation to the weak closed end of the straight pipe is relatively large(maximum 33.17 m/s, 0.31 μA), all differ by an order of magnitude. The peak temperature of each section is the branch 1042K> branch pipe 928K> straight pipe left side 793K> straight pipe right side 669K. The peak over-pressured value of each section is the branch pipe is 0.162 MPa>the right side of the straight pipe is 0.135 MPa>the left side of the straight pipe is 0.036 MPa. During the propagation of the detonation flame to the closed end, the reverse flow phenomenon occurs due to the negative feedback of the compression wave. Especially during the propagation to the branch port, due to the existence of the wall of the bifurcation, under the combined action of the negative feedback of the compression wave and the positive feedback of the high temperature gas product, the flame presents a state of oscillation.