Abstract: In order to study air leakage laws in goaf and gas migration laws under the action of air leakage in complex flow field formed by U+L type ventilation and gas drainage, based on the theory of similar simulation, U+L ( two into one back ) with high level borehole group gas drainage model is established in laboratory. Using energy measurement, tracer technique, the gas concentration distribution and other technical means, air leakage in goaf and gas migration laws under this mode are obtained.