This paper makes a systematic research on the collapse process simulation of masonry arch bridge based on OpenSees.It includes the following aspects:（1）Merits and demerits of small strain unit and large strain unit in the application of bridge collapse simulation are compared.（2）The TLFD8nBrick unit is secondarily developed by adding the mass matrix and its correctness in the dynamic calculation is verified.（3）The collapse process simulation of Di Xi Tuo Jiang Bridge is completed using the TLFD8nBrick unit.（4）The post-processing technology like calculation result nephogram and element birth and death display for finite element analysis of the collapse process is discussed.The results indicate that it will lead to calculation result distortion using small strain unit

so it can′t simulate nonlinear problems of the collapse process.What′s more

the TLFD8nBrick unit can be used for structural dynamic calculations after secondary development

and it can realize the collapse process simulation of the bridge.In addition

the calculation result of program developed by C#and VS.net 2005conforms well to Abaqus and its display efficiency of nephogram is high.Moreover

the display module of element birth and death can dynamically show the bridge collapse process

which provides help for the analysis of the cause of accident.