The Logistic model is improved for the description of severe acute respiratory syndrome (SARS), which is infecting all over the world especially in China. The model simulates the situations of SARS in different countries and in different provinces of China. The results reveal the asymmetrical phenomenon of the infection of SARS. The conditions that cause the infectious disease in natural circumstance and the factors that added by human for the control of SARS are considered in the model. The different measures, which are used to control the disease, can lead to different results. The phenomenon of super-spread events (SSEs) is also discussed.