Magnetic fluid seal structure is analyzed by the finite element method in this article. On the basis ofresearch on the tooth-shape of single stage seal. a new type of tooth-shape of multistage seal is suggested.Through calculation. it’s seal pressure can be increased by more than ten percent comparing to the traditionalrectangle tooth-spape. And the design ranges of all parameters of the magnetic circuit with this type oftooth-shape are offered in the end.