The invention discloses a seal joint used for connecting a bamboo-like prestressing force flat mouth plastic pipe with bolts and an exhaust pipe. The seal joint is formed by carrying out butt joint on a first half flat mouth pipe and a second half flat mouth pipe; the butt joint face is fastened and combined by bolt fastener groups; the exhaust pipe is arranged at the outer edge of the first half flat mouth pipe; two big grooves, two small grooves and sealing gasket grooves are respectively formed in inner rings of the first half flat mouth pipe and the second half flat mouth pipe; the two big grooves are respectively formed in two sides of the length middle points of the first half flat mouth pipe and the second half flat mouth pipe; the two small grooves are respectively formed in outer sides of the two big grooves; one sealing gasket groove is formed in each side of each big groove; and a flat mouth sealing gasket is arranged in each sealing gasket groove. The seal joint has the beneficial effects that the flat mouth sealing gaskets press two sides of a big flat mouth rib wrapping the bamboo-like prestressing force flat mouth plastic pipe; the construction sealing effect is good; the duct grouting compactness and plumpness are facilitated; the operation of fixing the seal joint by the bolts is simple and convenient; and the grouting quality can be improved by the exhaust pipe.