Abstract: For ordinary training institutions and employees of agricultural machinery production enterprises in underdeveloped areas, the common thermal cutting methods such as oxygen acetylene cutting and air plasma cutting have great advantages. Due to the high cost and high risk of oxygen acetylene cutting, a simple semi-automatic steel plate cutting device is designed based on the air plasma cutting technology. The device mainly consists of plasma cutting power supply, gas supply system, semi-automatic high-speed plasma cutting walking car, flexible plasma cutting gun fixture, plasma cutting workbench, etc. Through the prototype design and experimental verification, the cutting device is continuously optimized to achieve cutting of the welding test plates with grooves. It provides great convenience for welding skill training of the welding operators, and can also save costs for training new welding workers in small and medium-sized enterprises.