Abstract: The paper study on the “U” and “U+L” type ventilation system by the offshore module “Test Rig of Three-dimensional Flow Field”. By changing the distance between connection roadway and working face, the pressure between the intake airwayand return airway, we have analyzed the theregularities of gas distribution law of gob under different parameter conditions .The experimental results show that the gob air leakage intensity is linked with the pressure between the intake airway and return airway. High concentrations gas zone mainly concentrated in the compaction zone side of return air roadway.It's location and range along with the change of ventilation parameters change. We can focus on extraction from the zone in the construction site.If shorten the distance between connection roadway and working face, to some extent we can control the range of high concentrations gas zone in goaf area.