Abstract: In order to improve the precision and reliability of welding arc sensor in narrow gap, as well as to research the principle of arc sensor characteristic parameters influenced by the distance between welding torch and the side wall, by measuring the torch position using high precision laser displacement sensor, an experiment system for swing arc sensor which can simultaneously acquire welding voltage, welding current, welding torch swing position and arc image four signals was developed based on TMS320F2812 and Labview. Experiment was carried out by the welding method of P-GMAW. It was proved by the experiment that the established system is reliable and effective. The system has laid the necessary foundation for the further study of the characteristics of the narrow gap oscillating arc sensing.