Provided is a closed-loop internal circulation device for gas collection in the solid-liquid separation process. The closed-loop internal circulation device is composed of a compressed gas storage tank, a pressure regulating valve, a pressure transmitter, a check valve, a pressure exhaust drying valve, a reverse blowing valve, a clustered type reverse blowing filter, filter elements, a slagging valve, a slurry drying machine, a slag conveyor, a first-stage gas-liquid separator, a first-stage coalescence element, a gas scrubber, a spray assembly, a conveying pump, a second-stage gas-liquid separator, a second-stage coalescence element and an efficient gas filter. The slurry drying machine which operates in a sealed mode collects slagging filter cake and slagging gas, further drying treatment is conducted on the filter cake, and disorderly release of the gas and dust is avoided; gas-liquid coalescence separation is conducted on the gas through the gas-liquid separators, direct exhaust of atomized gas is avoided, effective coalescence collection of liquid mixed in the gas is achieved, and subsequent treatment burden is reduced; the gas is separated through inclined type corrugated plate screens or filler, spraying absorption is conducted on poisonous and harmful gas through the spray assembly, and damage caused by direct exhaust of the poisonous and harmful gas is avoided.