Abstract: The model of porthole extrusion in corner welding chamber of magnesium alloy pipe was established by combining shunt extrusion and corner extrusion. The deformation of welded metal was increased by corner shear. The influence of angle on the temperature, effective strain and hydrostatic pressure of weld metal in weld chamber was studied by using finite element method. The results show that within 100°-120° corner, with the increase of the angle, the strain of the welding metal increases and the pressure in the welding chamber increases gradually, which helps to improve the welding quality. The temperature of the metal welded by angle deformation increases, and the temperature in the welding chamber does not change obviously when the angle increases.