An LED light string includes a socket, electrical wires, and an LED-based luminous element. The LED luminous element has two conductive terminals respectively set in abutting contact with or to pierce through the electrical wires. The socket is composed of two unsymmetrical casing members. The electrical wires and the luminous element are first placed in the first casing member and then, the second casing member is fit to and attached to the first casing member. Ultrasonic wave is then applied to achieve secure coupling of the light string.