In order to solve the problem of the influence of different ignition positions on the characteristics of oil and gas explosion in the T-shaped pipeline, the flame propagation and pressure laws of ethanol gasoline vapor explosion under different ignition positions in the T-shaped pipeline were revealed through experimental studies. The results showed a quadratic relationship between the maximum overpressure (Pmax) and the dimensionless distance (Ip/D) between the ignition and the vent in T-shaped pipelines, significantly different from the positive linear correlation in straight pipelines. In a T-shaped pipeline, the right flame (towards the open end) does not form the “tulip flame”. When the distance between the ignition and the closed end is ≥ 300 mm, the left flame (towards the closed end) forms the “tulip flame”. The explosion overpressure undergoes periodic oscillations at different ignition positions. The closer the ignition is to the vent, the earlier the oscillation occurs, and the smaller the amplitude. The number of overpressure peaks in the explosion synchronously decreases due to how the flame enters the branch pipe. After the Ip/D is less than 4.75, there is little change in the maximum overpressure. The research can provide data reference for further understanding the evolution of explosions inside T-shaped pipelines and vents design.