A flexible decoration light string comprising multiple luminaries being connected with multiple electrical conductors in series, parallel or series and parallel to form rectangular lighting strings, by means of insulator along with said rectangular lighting strings under the way of longitudinal direction to contain and seal the luminaries and the electrical conductors within in said insulators, thus the luminaries and the electrical conductors being isolated to outside to form a flexible decoration lighting strings, then one or both ends of said strings connected to the connectors to form a circuit loop.