A gasflow distribution device includes an outer pipe, a gland, a filter screen, and a filling block with a pore structure. The outer pipe is a hollow outer pipe, used for placing the filling block, with an open upper end and a lower end with a bottom of which the center part is provided with a bottom hole, wherein the filling block is sealed to an inner wall of the outer pipe. The gland has a bottom end provided with a circular groove for setting the filter screen, and a top end distributed evenly with a plurality of top holes through the gland. The gland is connected to the outer pipe. The device can distribute gasflow proportionally, and can be used for separate-layer gas injection.