Disclosed is an LED light string manufacturing method, as well as an LED light string manufactured with the method, which generally involves four components that are assembled through three operations or steps to allow for automatic mass production of LED light strings thereby saving material cost and increasing assembling efficiency. The four components include an upper housing member, a lower housing member, electrical wires, and an LED-based light emission element (with or without a cover). Two conductive pins of the LED-based light emission element are fixed to conductors of the electrical wires through welding and are then disposed between the upper and lower members of the housing, which are subjected to ultrasonic fusion for secured combination thereby covering and housing the electrical wires and the LED-based light emission element therein in one operation. The method is simple and very efficient so that the process is simplified and the cost reduced.