The structure of the plasma sheath in an oblique magnetic field was investigated with the fluid method. In various different magnitude and directions of the ma g netic field, the electron and ion density distribution, ion flow velocity, elect ron potential and Bohm's criterion have been calculated. It is shown that the magnetic field has obvious effect on the plasma sheath. Under the action of electrostatic and Lorentz forces, the ion flow makes a helical movement, and the ion densi ty distribution fluctuates.