Abstract: The hypothesis of velocity linear distribution in wedge-shaped gap is often used to analyze the fluid field in high speed magnetic seal. But the result can not satisfy Navier-Stokes equation completely. So, two new methods are proposed to deal with the problem. One is based on the hypothesis of linear distribution of magnetic fluid velocity on the boundary, the other solves Navier-Stocks equation by extending control region in analysis. All the data is get by numerical calculation based on magnetic field method analysis. The results show that the velocity distribution derived by new methods can satisfy all the kinematics equations. The results obtained by the two new methods are very close in any case,and they are lower than the result obtained by the old method at high speed.