Abstract: A lamp head for decorative light string includes a luminous body, a pair of wires, a lamp base and a lamp shade, the luminous body electrically connected with wires, the lamp base formed by injection moulding and covers part of the packaging body and part of wires and electrode pins that between the packaging body and the wires, the lamp shade is assembled with the lamp base. The lamp base is provided with a plurality of holes, which connect the inner space of the lamp head with the outer space of the lamp head. Thus, water vapor produced in the inner of the lamp head can be expelled freely from the holes, so the decorative light string can remain normal operation to extend its life.