In order to improve the pressure capability of reciprocating sealing structure with magnetic fluid, the L 16 (4 5 ) orthogonal test design and the numerical simulation with the finite element method. were combined to optimize the sealing structure. In the process of orthogonal test design, five factors, four levels and the corresponding orthogonal table were selected. The magnetic field distribution of each orthogonal test was calculated and analyzed by finite element method. The results of orthogonal test were statistically analyzed by using range analysis and variance analysis and it shows that the simulation result of pressure capability of the optimal scheme is the best result in the test simulation analysis. The results showed that the pressure capability of the optimal scheme is about 0.91 MPa higher than that of the initial reciprocating seal with magnetic fluid.