The invention relates to an automatic welding machine of a DC wire. The machine comprises a wire cable transmission device, a cable cutting device, a wire cable cutting stripping device, a DC connector clamping device, a solder conveying device and a wire welding device. According to the automatic welding machine of the DC wire, firstly, a chain type conveyor belt drives a wire cable transmission seat to transmit the wire cable; secondly, the DC wire cable is treated by cutting and straightening along the center line through the wire cable cutting device; thirdly, the DC wire cable is subjected to head cutting and stripping through the wire cable cutting stripping device, and the length difference adapted to the welding device is generated at the same time; fourthly, the DC connector clamping device transfers a DC connector and positions the DC connector to a welding station, and the welding parts of DC connector are respectively positioned at the inner sides of a positive wire head and a negative wire head of the DC wire cable end; fifthly, the positive wire head and the negative wire head of the DC wire cable end are respectively welded to the welding parts of the DC connector through the wire welding device; therefore, the automatic welding is realized; the production efficiency is greatly raised; the product difference is lowered down; the uniformity and the product quality are greatly improved.