The invention relates to an all-fiber low-pressure gas cavity system. The all-fiber low-pressure gas cavity system comprises a hollow fiber, a left end tapered solid core fiber, a right tapered solid core fiber, a left end hollow fiber and solid core fiber butt joint and encapsulation module, a right end hollow fiber and solid core fiber butt joint and encapsulation module and a gas cavity inflation and deflation module; the hollow fiber and the left tapered solid core fiber and the right end tapered solid core fiber are subjected to butt joint and encapsulation through the left end hollow fiber and solid core fiber butt joint and encapsulation module and the right end hollow fiber and solid core fiber butt joint and encapsulation module respectively; and the left end hollow fiber and solid core fiber butt joint and encapsulation module and the right end hollow fiber and solid core fiber butt joint and encapsulation module are closely connected with the gas cavity inflation and deflation module, so that vacuumizing, inflation and deflation operation as well as internal gas pressure monitoring can be performed on the gas cavity of the hollow fiber. The invention also provides an all-fiber low-pressure gas cavity realization method carrying out all-fiber encapsulation by adopting the above the all-fiber low-pressure gas cavity. With the realization method adopted, a low-loss, high-strength and long-term-stability all-fiber low-pressure gas cavity system can be realized, and the method has a bright application prospect and an important application value in all-fiber infrared gas lasers.