The duplicate checking rate of ordinary papers is generally required to be lower than 30%. The specific requirements of different schools may be slightly different, for example, key institutions may require less than 15%. When re-checking journal articles, the requirements of core journals are usually high, ranging from 5% to 10%, while the requirements of ordinary journals vary greatly, ranging from 5% to 30%. In this paper, we should pay attention to different duplicate checking systems, which have different comparison databases and algorithms.