Underground and ground integrated drainage system and method

The underground and ground integrated liquid drainage system comprises an underground liquid drainage system, the underground liquid drainage system comprises an oil pipe, a sleeve, an underground shock absorber, a ball plug, a gas production tree, an automatic ball throwing barrel and a 1 # automatic control valve, and the upper portion of the gas production tree is connected with an in-station liquid drainage system; the in-station liquid drainage system comprises an in-station gathering and transportation pipeline, an in-station gas-liquid separator, a liquid separation pipe and a 2 # self-control valve, and the downstream of the gas-liquid separator is connected with the out-station liquid drainage system; the off-station liquid discharging system comprises an off-station gathering and transportation pipeline, an automatic ball collecting barrel, a downstream gas-liquid separator, a ball collecting shock absorber, a bypass pipe, a third self-control valve, a fourth self-control valve and a fifth self-cont