Abstract: Based on the geometry nonlinearity of four-link mechanism of Pall frictional damper(PFD), the influence of buckling force of braces, brace stiffness and slip force on the hysteretic behavior of an improved PFD T-shaped cone plate frictional damper(TFD)is analyzed. On the one hand, it is verified strictly that the hysteretic behavior of TFD(or PFD)is not influenced by the buckling force of braces. On the other hand, some new phenomena are revealed. Firstly, the tension force of the braces does not keep constant but increases remarkably after the slipping of TFD. Secondly, the maximum tension force of the braces has relationship with brace stiffness, and the greater is the brace stiffness, the greater the maximum tension force of the braces is.