This technique is a two -way rotation is from pump sending fluid dynamic pressure type mechanical seal, need assist circulation system to assist work in order to overcome present two -way rotatory fluid dynamic pressure mechanical seal, lack the defect that anti granule disturbed the ability, it is by the rotating ring, O shape circle for the rotating ring, quiet ring, quiet O shape circle for the ring, a spring, the stationary seat is constituteed, the rotating ring terminal surface includes the helicla flute, sealed weir and sealed dam, quiet ring terminal surface external diameter side is processed into the conical surface, adopt the fluid pump the mode of going into with the fluid pump produce bu tong soon to the time the fluid dynamic pressure, rotating ring forward rotation comes from sealed chamber, is covered with the medium of helicla flute through the drainage pore, is added quick fast fluid by the convex surface of helicla flute, the centrifugal force effect down, the edge concave surface moves and pumps to sealed chamber to rotating ring external diameter side flow, rotating ring reverse rotation, the medium of sealed intracavity wedge along the concave surface of helicla flute, and the pump goes into to the helicla flute root to become high -pressure fluid to rotating ring internal diameter side flow moves, under the pressure differential effect, flow again through the drainage pore and into seal the chamber.