Alternanthera philoxeroides is a perennial herbaceous amphibious aquatic weed of the family Amaranthaceae, native to South America. It was first found in Shanghai, China in 1892. After a stagnant phase of 50 years (1890s-1940s), A. philoxeroides spread rapidly throughout areas of central and southern China, and the range is still expanding. It is one of the most harmful and widely distributed alien species in mainland China. We applied Genetic Algorithm for Rule-Set Production (GARP) ecological niche modeling to predict the species’ potential range in China on the basis of occurrence points within colonized areas whereA. philoxeroides had reached equilibrium. Environmental factors such as slope, flow accumulation, mean annual temperature, annual precipitation greatly influenced the size of A. philoxeroides’s potential range, while parameters such as solar radiation and elevation had little impact. Areas that we predict to have potential for invasion were still larger than those areas that had been invaded. Therefore,A. philoxeroides is predicted to continue to expand in China. Most Chinese provinces excluding Tibet, Qinghai, western Sichuan, southern Xinjiang, western Gansu, north-eastern Inner Mongolia, Jilin, Heilongjiang and Hainan are likely to be invaded. Because they are adjacent to areas that had been invaded, Shaanxi, Shanxi and south-eastern Gansu were most liable to be invaded; hence urgent measures should be taken there to prevent this species from further spreading.