应用系统动力学模型，定量地分析“早发现、早隔离、早治疗”措施，对于控制SARS疾病扩散与传播的重要性。结果表明，“得病后入院时间”与“隔离措施强度”对于SARS疫情态势发展，具有很大的敏感性与相关性，其中得病后的患者几时去医院治疗，对于疫情的控制具有更重要的意义。同时应用动力学模型，对北京的SARS疫情进行分时间段的模拟与SARS实施控制因素影响分析，结果表明，2003—04—20以后一段时间内实行的各种控制措施，以及5月1日—5月5日的长假对于北京SARS疫情的控制是非常有效的；而4月27日左右北京市社会上未得到有效控制的SARS病人数达到高峰，是最危险的时期。5月20日以后，北京的SARS疫情基本保持在低发的平台期，但是如出现较多的外来SARS病例输入，而内部隔离强度又减弱、社交活动增加等情况下，北京SARS疫情可能会有一定程度的波动与反弹。

A Severe Acute Respiratory Syndrome (SARS) spread model based on System Dynamics (SD)approach is implemented to do the quantitative analysis of the critical importance of control policies such as early report, early quarantine, and early hospitalization to control further SARS epidemic spread. Using this model, a case study on Beijing SARS epidemic situation is conducted. The simulation results show that the onset-to -hospitalization interval and effective quarantine are two key factors in SARS transmission. Furthermore, the shortening of onset-to-hospitalization interval should be given the highest priority. In addition, a period based simulation is carried out to analyze SARS spread and control effectiveness in Beijing. The simulation outcome demonstrates that various control measures after April 20,2003 in Beijing and the public holidays starting from May lst to May 5th have a significant impact on containing the epidemic situation. The most dangerous days, around April 27, when the number of uncontrolled SARS patients in the society reached at its peak, can also be calculated. The SARS infectiousness number newly reported in Beijing has been at a low level since May 20. But simulation experiments describe that it may fluctuate with import of SARS infectiousness from outside Beijing, weakening of quarantine, more social activities, and so on.