In order to study the energy dissipation performance and damage evolution of X-shaped mild steel dampers under large deformation,6 groups of specimens were designed for experimental study of ductile fracture under unidirectional and cyclic loads,and the failure process and hysteresis curve of the dampers were analyzed.Using Lemaitre-Chaboche hybrid strengthening model,the finite element simulation of mild steel dampers with and without the steel microdamage model based on stress triaxiality was carried out under different working conditions.Comparing the finite element simulation results with the test results,the analysis results show that the neck is the weak position of the X-shaped energy-consuming mild steel damper,which is most prone to concentrated damage or even destruction.The load-displacement curve of finite element simulation considering steel damage criteria is more consistent with the test results,which can characterize the bearing capacity and stiffness degradation of mild steel dampers,and predict the damage evolution process and fracture location of mild steel dampers more accurately.