Smooth cordgrass (Spartina alterniflora) is one of the harmful quarantine weeds in China. Since its first introduction in China in 1979, this alien species has spread rapidly and damaged local ecological environments. Research to predict a suitable new area is an important step for management of the species and to prevent a further spread. In this study, Spartina alterniflora’s ecological niche was modeled using the application MAXENT. Analysis was based on species’ current distribution. The investigations of this study were two-fold. First, a large-scale global investigation (outside China) was conducted to predict suitable areas in China by comparing global and Chinese records of the species. In the second set, the combined records were used to predict suitable areas in the Jiangsu Province. The model’s accuracy was evaluated by Receiver Operator Characteristic (ROC) curve. The areas under the ROC curve (AUC value) were all over 0.95, which indicated high predictive ability of this model. In the large scale prediction, Shanghai, Zhejiang, Fujian, Guangzhou, Guangxi and southern part of Wuhan, Jiangsu and Anhui were all potentially endangered by S. alterniflora invasion. On the smaller scale, the prone to invasion areas were mostly concentrated on southern part and some coastal areas of Jiangsu Province, where the precipitation and temperature were appropriate for this grass. Because of S. alterniflora has high dispersal ability and human induced history, the potential distribution areas in China are considerable and it may invade more areas, in result spreading faster in the future. To prevent further invasion and spread, an early eradication program should be adopted in the newly invaded areas. Meanwhile, the monitoring programs should also need to be applied in potential survival areas, especially in coastal harbors, airports, and tourism areas which are highly vulnerable to S. alterniflora invasion.