Abstract: Taking plasma arc as the research object,a two-dimensional axisymmetric finite element mathematical model of the tip was established and the model was meshed by Anysy-workbench software under basic assumptions. Based on the hydromagnetics and arc plasma theory,the control equations and boundary conditions of the air plasma arc model were established. In the Flunent software,the user-defined equation UDF command was used to add the source term of the arc control equation and the physical parameters of the air plasma,and the UDF command was imported to compile and solve the arc model. The simulation results showed that with the increase of environmental pressure underthe same welding current,the maximum temperature of the air plasma cutting arc showed a downward trend. Based on the 2 MPa high pressure welding test chamber,the plasma arc cutting test system in high pressure environment was established. The system mainly consisted of high pressure plasma arc cutting power supply,automatic cutting car,arc monitoring device and so on. Through the designed horizontal output transformer,stable arc starting under 0. 4 MPa was achieved. Based on this,plasma arc cutting experiments under normal pressure and high pressure were carried out,and the influence of pressure on the shape of plasma arc was studied.