Researchers have been studying the magnetic fluid seal of small gap in the past. In order to meet the static seal requirements of large gap in aviation, aerospace, metallurgy, and so on. We set up the experimental rig of magnetic fluid static seal and designed the static seal of magnetic fluid. In the experimental rig, we studied the static seal of magnetic fluid and obtained the relationships among the burst pressure and the amount of injection of magnetic fluid, seal gap, temperature and magnetization in the experimental rig. In theory, we calculated the distribution of magnetic field under the seal gap and reasoned sustained pressure and temperature and calculated the burst pressure in different gaps and different saturation magnetization. We analyzed the experimental and theoretical results in detail. The theoretical analysis and tests indicated that magnetic fluid seal of large gap and large diameter can sustain a definite pressure and meet the requirements of practical problems.