Abstract: Plasma arc cutting as a common thermal cutting method is widely used in aerospace, navigation and many other fields. Through the optimization and upgrading of the plasma arc cutting machine, a high-pressure plasma arc cutting system was successfully built, and finally the non-high-frequency arc initiation technology was used to achieve the stable arc initiation with an environmental pressure of 0.1-0.7 MPa, which can put forward a new idea to solve the problems of nonarcing and difficult arc initiation in high-pressure environment. According to the comprehensive scoring method to measure the cutting quality, the optimal cutting process parameters with environmental pressure of 0.1 MPa, 0.4 MPa and 0.7 MPa were obtained by designing orthogonal tests. The results show that the cutting current and cutting speed have a great influence on the cutting quality when the environmental pressure is 0.1 MPa; when the environmental pressure is 0.4 MPa and 0.7 MPa,the air supply pressure becomes the main factor affecting the cutting quality.