The utility model discloses a foam concrete channel prefabricating device which comprises a front-end capsule for blocking the front end of a hole collapse section, a rear-end capsule for blocking therear end of the hole collapse section, and an air pipe device for connecting the front-end capsule with the rear-end capsule, the air pipe device comprises a plurality of connecting air pipes communicated with the front end capsule, one end of each connecting air pipe is provided with a spherical top end, and the spherical top ends extend into the rear end capsule. According to the utility model,the front-end capsule, the rear-end capsule and the air pipe device are arranged; the prefabricated channel is stable and firm; the gas extraction requirement can be met, the prefabricated channel iscylindrical, the circulation resistance of gas in the channel can be reduced to the minimum, due to the arrangement of the connecting gas pipe and the spherical top end, the connecting structure of the front-end capsule and the rear-end capsule is simple, and the capsules are connected more tightly, cannot fall off, and are reliable, stable and good in using effect after being inflated.