The invention provides a manufacturing method of a photovoltaic welding strip and a tin coating machine thereof. The method comprises the following steps: A, carrying out a simple pretreatment on a copper strip; B, sending the pretreated copper strip into a plating solution of a tin furnace for tin coating, when tin coating, carrying out an ultrasonication to the copper strip with ultrasonic waveemitted by an ultrasonic wave transducer arranged above the tin furnace; C, blowing tin with inert gases, and D, receiving materials. According to the invention, by adding ultrasonic wave in the tin coating process, tin liquor can rapidly form an alloy layer of copper and tin on the surface of the copper strip by the sound pressure effect of the ultrasonic wave, the production efficiency of the photovoltaic welding strip is increased, the transporting speed of the copper strip reaches to 10-80m / min; by removing grease and oxide layer on the copper strip surface, reducing the usage of chemicalreagents, simplifying the pretreatment before coating, and utilizing the ultrasonic wave to crush clusters of tin oxide, the defects of pinhole and tin slag of the welding strip is prevented, the quality of the welding strip is improved, and the production efficiency is raised greatly.