This article takes the public safety events in closed location as the research object,takes the entropy and dis- sipative structure theory as the guide idea,uses the entropy theory to describe the emergency's moving mechanism,puts the causes lead to the event happen as the increase factor of the entropy,while the prevention means and the control measures as the decrease factor of the entropy.Then it uses the dissipative structure theory to resolve the entropy in- creasing problem,achieves the aims to minimum of the entropy and makes the system get back to balance again.