Abstract: In a tier building or tall building with frame structure,the total building structural system consists of stairs structure and frame structure.This total structural system may be called frame-stairs system.Unreasonable joints of stairs structure can bring some bad characteristics of this frame-stairs system.Such unreasonable stairs may be destroyed badly in earthquake,and escape way may be cut off.The bad characteristics of this structural system were shown by push-over analysis.Based on the conclusions of push-over analysis,a kind of reasonable joint of stairs structure in frame-stairs system was put forward.By this kind of joint,the way transfering horizontal loads down in stairs was cut off.In this case,stairs elements won't participate in transfering down horizontal earthquake actions of building,and the destruction of stairs elements might be avoided.Adopting such structure,it may be possible for stairs to become safety island.