Abstract: Welding current and voltage are important parameters that affect welding quality. In order to improve welding quality, a method of on-line detection and accurate control of welding current and voltage based on visual sensing technology has been studied in this paper. Firstly, the preprocessing of welding current and voltage image is studied, and the character image corresponding to welding current and voltage is segmented. Then, a recognition method of corresponding characters of welding current and voltage based on projection feature is studied, and the recognition of welding current and voltage is further realized. Finally, the automatic control method of welding current and voltage based on expert control is studied, which can improve the stability, accuracy and rapidity of automatic regulation of welding current and voltage. The experimental results show that using the method studied in this paper, the accuracy of online identification of welding current and voltage is higher than 99.75%. It can achieve automatic detection and control of welding current and voltage before and during welding, and can adjust the weld bead size online as needed, which helps to improve the automation level and welding quality.