The invention relates to an experimental device for researching micro-leaking of gas in underground oil and gas reservoir through stratums. The experimental device comprises a simulation chamber, a gas cylinder and at least two layers of simulated stratums superposed up and down, and a soil layer positioned uppermost, wherein each simulated stratum comprises a direct covering layer with small hole penetration, and an overlying stratum with large hole penetration and positioned above the direct covering layer, and each direct covering layer is provided with a gas outlet. The experimental device can be used for simulating the micro-leaking rule and near-surface abnormal distribution of gas in a plurality of oil and gas reservoirs underground, so as to obtain theoretic knowledge for guiding the oil and gas earth chemical exploration practice; the experimental device can conduct oil-gas secondary migration simulation and mechanism study thereof; the experimental device can conduct the closure study of the oil and gas reservoir covering layer; the experimental device can conduct oil and gas consumption quantity simulation study, thus providing parameters for the calculation of resource quantity.