Abstract: As the Federal law enforcement officer, Federal air marshal had searched and arrested without a warrant for several times. And, we can analyze the constitutionality of these measures from three aspects. First, significant aviation safety is the basic interests of warrant exception because an air marshal mainly deals with serious hijack or terrorists attacks. Second, the special circumstance of cabin and critical condition satisfies the condition of "emergency exception" of warrant. Third, even meeting the condition of warrant exception, an air marshal also needs to satisfy the "probable cause" requirement of Constitution when they make a search or an arrest.