When polymer solution is injected into reservoir, if the radius of polymer molecule thread is much larger than the radius of pore throat, it will cause the blockage of polymer in reservoir pore. Selecting a typical block in Sabei oil field, sampling the blocked injection wellbore backflow, and analyzing the composition of backflow by laboratory, it is determined that the main component of backflow blockage is polymer soft micelle. According to the geological structure, sedimentary facies, reservoir property of geological data, the geological model of plugging wells was establish，the concentration of polymer distribution in the reservoir was utilized, the polymer solution flowing trajectory was simulate and the distance of the polymer blockage was confirm. The advancing distance of direction provides a basis for improving the blocking condition of injection wells and taking pertinent measures.