The fuction and structure of the atrium are very complexity. If fire occurs,it will bring great loss. Forms of atrium and the characters of gas flow are analyzed, fire detectors are classified. Performance, applicability and the cause of wrong alarm of fire detector are compared comprehensively. According to the performance of detector, the shape of atrium and the character and possible danger of fire,a method of selecting fire detector to be applied to atrium is given. The validity of the method is explained clearly with an given example.