A magnetic fluid sealing device, includes first pole teeth and a first magnetic fluid adsorbed on the first pole teeth functioning as a first line of defense for sealing, as well as second pole teeth and a second magnetic fluid adsorbed on the second pole teeth functioning as a second line of defense for sealing. The second pole teeth of the magnetic fluid sealing device are arranged on the permanent magnet or the flux sleeve. Since the flux sleeve is fitted over the permanent magnet, the arrangement of the second pole teeth can ensure the ability of the pole shoe to absorb the magnetic fluid, and also can make full use of a length of the permanent magnet in the axial direction of the rotating shaft. Therefore, the magnetic fluid sealing device is effectively improved in the sealing effect and the pressure resistance without increasing its axial length.