The invention provides a welding method of a power transmission line. The welding process of the power transmission line comprises the following steps: firstly flatly cutting two end surfaces of the power transmission line required for welding, opening rod-penetrating bolts for an upper half ring and a lower half ring, inserting two ends of the power transmission line joint into a thread hole, clamping the upper half ring, the lower half ring and the power transmission line while maintaining the rotating gap through fastening nuts, pulling a weld handle to circumferentially move along the power transmission line, welding joints at two ends of the power transmission line into one through the weld handle to finish the welding process. The adopted welding device is as follows: the upper half ring and the lower half ring are opposite to each other and connected with each other by using the rod-penetrating bolts and the fastening nuts through combined columns, the upper half ring and the lower half ring are buckled to form the thread hole, and the weld handle is installed on the upper half ring or the lower half ring. By adopting the method for welding the power transmission line, the connection is firm, and the operation process is simple, fast and convenient. The method is suitable for the joint connection of power transmission line.