CO_2 flooding not only can seal carbon dioxide to control global warming,but also can improve the recovery. So it has very important research significance. However except for monitoring carbon dioxide production,the process of oil displacement becomes a weak link,which restrict the further development of CO_2 flooding. The seismic method as a relatively mature geophysical exploration method,has technical feasibility to describe the oil displacement process. This paper draws on the research achievements made in China and the rest of the world. Starting from basic research and using the actual data furnished from a pilot area at Shengli Oilfield, it analyzes,by means of fluid replacement and forward modeling,the physical parameter variation of rocks in the process of CO_2 flooding with respect to theoretical model as well as individual well data. Moreover,this paper also studies the pre-and post-stack seismic response characteristic variation pattern and comes up with milestone appreciation of seismic response characteristics in CO_2 flooding. The work of this paper may have a value of reference for research in seismic monitoring of CO_2 flooding.