The present invention relates to a kind of decorative light strings with combination tree, including a long trunk to be composed of many short pipes, the height of tree lamp can be adjustable by the number of the short pipe; base frame is to use a support surface to erect the base frame and has a center axis to support long trunk to stand up right straight; multiple branches connect with the long trunk; single or multiple set of light strings, composed of many lamp bulbs, lamp holders, electrical conductors and receptacles, to be fixed on the branches to establish tree light strings.