A process for controlling downhole gas in an abandoned mine, wherein the process comprises steps of: 1) before closing an abandoned mine, blocking branched drifts (1, 2, 3) with high downhole gas overflow at their joints with a main drift by squared stone walls and embedding pipes to extract gas and to pump inflowing water; 2) connecting the pipes embedded in the squared stone walls to extract gas with a downhole gas pumping pipe to form a downhole gas pumping pipe system, and then pumping accumulated downhole gas in an abandoned mine by an existing gas pumping system device on the ground; 3) communicating the blocked drift drainage water with main drift drainage water, constructing a water reservoir somewhere low on the bottom of the mine, forming a water drainage well bore from the ground to the water reservoir, and mounting a water drainage pump and a water pipe to pump inflowing downhole water to the ground, in order to achieve normal pumping of inflowing downhole water after the mine is closed; an inlet of the water drainage pump is put into 2/3 of a depth of the water reservoir; a water outlet for the branched drift (1, 2, 3) is formed in a lower side of the squared stone wall; the water outlet is in form of an overflow water seal; a water tank is constructed inside the branched drift close to the squared stone wall; the inflowing water in the branched drift flows into the water tank, when a level of accumulated water reaches an overflow height, the inflowing water flows out of the branched drift from the water tank; while gas in the branched drift will not escape from the water outlet; the inflowing water over flown from each branched drift flows into the water reservoir by a drainage ditch arranged in the main drift; 4) after finishing the above operations, for an adit inclined shaft, closing an entrance of the adit inclined shaft by building internal and external walls (19,21) with squared stones, cement and sand, with loess and clay filled between the walls, and embedding steel pipes that run into the mine in an upper portion of the entrance of the adit inclined shaft; and for a vertical shaft, blocking an entire entrance of the vertical shaft with steel-reinforced concrete cover plates, and embedding steel pipes in the center of the steel-reinforced concrete cover plates to enable the interior to communicate with the exterior; and the connection with the existing gas pumping system device on the ground achieves the pumping, control and utilization of gas in an abandoned mine; and 5) connecting the existing gas pumping system device on the ground with a downhole gas pumping main pipe to pump gas, thereby achieving the purposes of comprehensive control and utilization of downhole gas in an abandoned mine. 1) before closing an abandoned mine, blocking branched drifts (1, 2, 3) with high downhole gas overflow at their joints with a main drift by squared stone walls and embedding pipes to extract gas and to pump inflowing water; 2) connecting the pipes embedded in the squared stone walls to extract gas with a downhole gas pumping pipe to form a downhole gas pumping pipe system, and then pumping accumulated downhole gas in an abandoned mine by an existing gas pumping system device on the ground; 3) communicating the blocked drift drainage water with main drift drainage water, constructing a water reservoir somewhere low on the bottom of the mine, forming a water drainage well bore from the ground to the water reservoir, and mounting a water drainage pump and a water pipe to pump inflowing downhole water to the ground, in order to achieve normal pumping of inflowing downhole water after the mine is closed; an inlet of the water drainage pump is put into 2/3 of a depth of the water reservoir; a water outlet for the branched drift (1, 2, 3) is formed in a lower side of the squared stone wall; the water outlet is in form of an overflow water seal; a water tank is constructed inside the branched drift close to the squared stone wall; the inflowing water in the branched drift flows into the water tank, when a level of accumulated water reaches an overflow height, the inflowing water flows out of the branched drift from the water tank; while gas in the branched drift will not escape from the water outlet; the inflowing water over flown from each branched drift flows into the water reservoir by a drainage ditch arranged in the main drift; 4) after finishing the above operations, for an adit inclined shaft, closing an entrance of the adit inclined shaft by building internal and external walls (19,21) with squared stones, cement and sand, with loess and clay filled between the walls, and embedding steel pipes that run into the mine in an upper portion of the entrance of the adit inclined shaft; and for a vertical shaft, blocking an entire entrance of the vertical shaft with steel-reinforced concrete cover plates, and embedding steel pipes in the center of the steel-reinforced concrete cover plates to enable the interior to communicate with the exterior; and the connection with the existing gas pumping system device on the ground achieves the pumping, control and utilization of gas in an abandoned mine; and 5) connecting the existing gas pumping system device on the ground with a downhole gas pumping main pipe to pump gas, thereby achieving the purposes of comprehensive control and utilization of downhole gas in an abandoned mine.