To study the mechanical performance of tied-arch bridge under structural defects and traffic increase，a limited element model of Panzhihua Luoguo Jinshajiang Bridge is established and analyzed.Firstly，common damage models and their influence factors are presented.Then，based on established engineering model，changes of suspender force caused by arch rib lineation defect，hanger lineation defect and boom failure are calculated and analyzed respectively.Calculation results show that，suspender forces are more sensitive to arch’s vertical defect than to its transverse defect.While，short hangers are more sensitive to lineation defect than long ones，and secondary moment and shear force in short ones are bigger than in long ones.The results also tells that single boom failure can fiercely change neighbor booms’ forces，at the same time，boom failure spreads faster in short boom area than in long boom area.Traffic increase accelerates structure’s fatigue fracture.