Underwater wet welding arc is an arc produced in liquid dielectric and is very different from that in terrestrial gas environment arc. In this paper,an underwater wet welding arc model are created from the angles of electrostatics and particle physics,and it divides the underwater medium into ionized bubbles,transition layer,and liquid layer. Considering the heat emission at the saturation current density described by Sommerfeld’s formula, the underwater DC arc discharge is simulated. The analysis results show the shape of the arc formed by the electron beam and its arc velocity map,and the influence of the arc’s own magnetic field on the electron beam trajectory under the effect of high energy and high current density accompanying the underwater wet welding process.The shape of the arc track is shrunk to a "bell shape".