Abstract: Biology and specificity of Puccinia spegazznii, a potential biocontrol agent of invasive weed, Mikania micrantha, were investigated under quarantine greenhouse in China. As an obligate parasite with short-cycled autoecious, it completed life cycle on Mikania mictantha by teliospores and basidiospores. It infected leaves, petioles and other vegetative organs of the host plant infected parts became chlorosis after inoculation for 4-5 d. Twelve to fifteen days later, yellow telia appeared from back of infected leaves. The infected leaves died and/or defoliated. Teliospore was yellow to brown color without dormancy. 72 species of plant, belonging to 29 families, 62 genera, were tested for infection. They were divided into 12 groups in the testing program. M. micrantha was used as CK plant in each group. Three replicates were settled. Inoculation method of the pathogen was in line with the sequence and regulation of the Centre for Agriculture and Bioscience International. Result showed that chlorosis spot appeared on Asparagus cochinchinensis, Eupatorium adenophorum, Elephantopus scaber and Helianthus annuus. However, no mycelium and hostorium were found. It is recognized that the fungus infected Mikania micrantha and M. cordata in China.