Abstract: The effects of structural parameters on the performance of magnetic fluid seal are researched on the basis of magnetic field analysis.The parameters include seal gap,structural parameters of pole tooth,structural parameters of permanent magnet and the number of teeth on the pole.In the process of magnetic field analysis,magnetic field method and unequally spaced net finite difference method are used to obtain accurate data.A qualitative explanation to the data is given by magnetic circuit analysis.In order to testify the theoretical research,an optimized magnetic fluid seal has been designed and tested.The experiment results show that the weight and size of the optimized seal are reduced by more than 50 percent.