Abstract:Parasite Cuscuta campestris Yunker was examined for controlling the growth and spread of harmful weed Mikania micrantha H. B. K. The experiments were carried out to estimate biomass production by sowing the seeds of M. micrantha in sample plots in Shenzhen Xianhu Botanic Garden where this weed grew densely, and for physiological study by cultivation of both plants in pots. The result exhibited that the leaf number, stem length, and biomass dry weight of individual of the host M. micrantha began to decrease after the host was parasitized for about 30 days. Such decrease was obvious after 2 months of parasitism, so did the photosynthetic rate (Pn), transpiration rate (E), stomatal conductance (gs), water use efficiency (WUE), chlorophyll content, and Fv/Fm. The parasite could spread rapidly extending to an area of 20 m2 with longest distance of 5 m within 2 months. The parasite hampered the growth and reproduction of the host and depressed it even to die. It is suggested that C. campestris might be a promising plant for controlling this weed.