Abstract: Starting out from the basic principles of welding, the resistances in the welding loop of the narrow lap welding machine were categorized into stable resistance and unstable resistance, which were detailed analyzed in this paper. It was pointed out that the main factors affecting the resistance in the welding loop of the narrow lap welding machine are the surface quality of the welding wheel, the pressure of the welding wheel, the height of the welding wheel, the track of the welding carriage, the flatness of the welding clamp, the material of the strip steel, the strip plate type, the cleanliness of the steel plate and the amount of lap etc. These factors will cause obvious variations in the resistance of the welding area, thus influencing the quality of the weld. Further suggestions concerning daily equipment maintenance and management were also given.

Key words: narrow lap welding machine, resistance, welding, strip steel