||We analyze the SARS epidemic data with the modified SIR model. This model is included the effect of latent period. We applied this model to study the epidemic behavior of SARS in Hong Kong. The reproduction number Ro is estimated which is larger than the pervious result. Also, the reproduction numbers in hospital Roh and community Roc are obtained by using the infection-to-onset and onset-to-admission distribution in medical paper. The effectiveness of various control measures is estimated, and hospital isolation seems to be the most important control measure on SARS. The same technique is used to study the SARS epidemic in Singapore and Canada. The Amoy Garden outbreak is studied by using a static model. With our model, we project the future epidemiological behavior of the disease if it appears again.