Therefore at the state of emergency take place, it is very important to regulate the administrative emergency power .

By researching the concept and constitutive requirement of public emergency to prevent SARS through legal means,this paper explains what administrative emergency power is.

To boost the legislation of emergency, we need a deep study of the constitutional roots, norms, nature and regulation of administrative emergency power.

The legal control to the state!emergency power, especially the administrative emergency power, needs to be theoretically studied.

Natural disaster law and environmental law are both independent law department,but there are some common legal questions,such as the protection and treatment of secondary disaster、the emergent administrative power and the act of God.

The administration emergency powers are needed to control and dispel the crisis,but it can shake citizen s rights,so to define the citizen s right in the sudden changes,to draw distinction,to establish the guarantee systems of procedure and relief mechanism are necessary so as to seek the balance between the administration emergency powers and citizen s right protection in the sudden occurrences.