An air blower tooth coupling oil leakage preventing device comprises a speed increaser output shaft, a trapezoid seal ring, an exhaust pipe, a tooth coupling, an air blower input shaft, a coupling seal housing, an oil spraying pipe and an oil return pipe, wherein the speed increaser output shaft is connected with the air blower input shaft through the tooth coupling and is arranged in the coupling seal housing, the trapezoid seal ring is arranged between the speed increaser output shaft and the coupling seal housing, the exhaust pipe is arranged on the coupling seal housing, and the oil return pipe is arranged at the bottom of the coupling seal housing. The air blower tooth coupling oil leakage preventing device has the advantages that the seal ring is trapezoid in appearance, the contact area of the seal ring is doubled and accordingly oil and oil gas leakage are prevented. The seal ring is made of a composite rubber material and can be resistant to high pressure and good in sealing effect, ageing and oil leakage phenomena are prevented after the air blower tooth coupling oil leakage preventing device is used for a period of time, the exhaust pipe is installed on the upper side of the coupling seal housing, the oil gas produced at high temperature can be smoothly discharged out, and oil leakage at the sealing position due to pressure produced in a box is prevented.