Abstract: OBJECTIVE To find out a optimal solution for existence and universality of positive samples in pooling sample assay for SARS-Cov-2 so as to provide a more effective and rapid detection method for nucleic acid screening of low-risk population. METHODS A mathematical model was built based on the relationship among time requirement, size of kits under the situation of different numbers of positive samples and maximum size of test sample during the pooling sample assay so as to seek the optimal test method from coding and non-coding method. Three circumstances including positive samples, single positive sample and multiple positive samples were explored, and the demanded quantity of test reagents was observed under the different circumstances. RESULTS The efficiency of box-marfa test method is higher when showing the existence of positive sample and single positive sample, and the efficiency of non-coding optimal block test method was higher when showing multiple positive samples. The demanded quantity of test reagents of the optimal block test method was superior to other methods. CONCLUSION The research result can be directly used for test of infection among low-density population, the box-marfa test method is suitable for situation of sufficient detection resources and checking out positive samples. The optimal block test method is suitable for situation of less positive samples and limited test resources as well as the situation of mixed test technique to be improved by a large margin. Taking the mixed test of 60 696 samples as an example, it can be used in a region with the positive rate less than 8.34%. The content of the research is suitable for low-risk and medium-risk regions and some of high-risk regions, it has significant application value in low-risk regions with insufficient test resources in initial stage of epidemic, regional screening in medium stage of epidemic and reginal time-limit test, and this method is also suitable for other virus samples for which mixed test can be carried out.