A design of light string comprises a bulb socket, a pair of conductive wires, and LED electrically disposed onto the bulb socket. The LED is incorporated with a pair of legs which are alternatively in contact with the pair of conductive wires, and then are sandwiched between a pair of first and second casings which jointly configures the light bulb. This configuration simplifies the assembling of the conductive wires and LED such that no need of solder or glue or contacts.