The reliable operation of the crankshaft seal used in the horizontal piston pump is an important part for the lubrication of the crankshaft bearing and the stable supply of the hydraulic support.A magnetic liquid sealing structure with single magnetic source and gradient tooth width was designed according to the magnetic liquid sealing theory.The numerical simulation method was employed to study the magnetic field distribution characteristics of the magnetic liquid sealing structure.The effects of different sealing gaps and rotational speeds on the pressure resistance of the seals were analyzed.The results show that the average pressure resistance of the gradient pole tooth width seal structure is increased by about 11% compared with the magnetic liquid seal structure with uniform pole tooth width.In the gradient tooth width sealing structure,the pressure resistance capacity of each pole tooth increases gradually with the increase of the distance between the pole tooth and the permanent magnet.The limit speed of the seal failure caused by centrifugal force gradually decreases with the increase of the seal gap.