The invention provides a cantilever type automatic tin soldering device. The device comprises an X-axis movement module, a Y-axis movement module, a rack and a product conveying assembly line, wherein the product conveying assembly line is installed on the rack, the X-axis movement module is installed on the rack through a supporting plate, and the Y-axis movement module is installed on the X-axis movement module. The device further comprises a Z-axis lifting module, an iron welding assembly, an iron welding assembly rotating device and a soldering tin supplying device, wherein the Z-axis lifting module is installed on the Y-axis movement module through a supporting frame, the iron welding assembly rotating device is installed on the supporting frame, the iron welding assembly is installed on the iron welding assembly rotating device, the solder wire supplying device is installed on the supporting frame, products to be subjected to tin soldering are fed into the product conveying assembly line and positioned, the iron welding assembly rotating device drives the iron welding assembly to rotate to an assigned angle, the soldering tin supplying device is used for conveying soldering tin to the iron welding assembly, and the X-axis movement module, the Y-axis movement module and the Z-axis lifting module are combined to drive the iron welding assembly to an assigned position for tin soldering.