The sweep scope of carbon dioxide in the reservoir is a key factor affecting the effectiveness of carbon dioxide huff and puff in tight oil reservoirs to enhance recovery. How to extend the sweep scope of the injected carbon dioxide in the reservoir is a new research topic. Using reservoir numerical simulation software, a theoretical model of carbon dioxide huff and puff in tight oil reservoirs was established. By monitoring the changes of reservoir pressure and carbon dioxide content during the throughput process, it was found that there is a low-pressure region that limits the sweep scope of carbon dioxide during the pressure equilibrium process, and on this basis, the effects of injection pressure, well stew time and huff and puff rounds on the sweep scope of carbon dioxide were analysed. The results show that the injection pressure is the main factor affecting the sweep scope of carbon dioxide, while the huff and puff rounds has less influence on the sweep scope of carbon dioxide.