Nucleic acid detection of SARS-CoV-2 plays an important role in the prevention and control of COVID-19. During the process of the nucleic acid detection of SARS-CoV-2, prevention of laboratory contamination is an important quality issue, which is a key factor to guarantee the quality of nucleic acid detection of SARS-CoV-2. There are many kinds of contamination sources in PCR laboratory, among which contamination caused by positive control is the most difficult to deal with in the experimental process. In this paper, the possible contamination of positive control during the process of nucleic acid detection of SARS-CoV-2 was analyzed and discussed in detail from the aspects of contaminating ways, causes, decontamination measures and effect monitoring, so as to provide some effective decontamination measures and countermeasures for PCR laboratory from the perspective of contamination from positive control.