The invention discloses a method for obtaining coding genes of gram-positive bacterium quorum sensing signal peptides. The method includes the following steps that 1, sequences are collected from genes of the quorum sensing signal peptides opened already,; 2, 16s rDNA sequences of strains are obtained; 3, a bacterium to be detected is compared with the sequences obtained in the step 2, and a genetic evolutionary tree is built; 4, sequence alignment is carried out on the coding genes of the gram-positive bacterium quorum sensing signal peptides of the bacterium obtained in the step 3, and a degenerate primer pair is designed; 5, the genomic DNA of the bacterium to be detected is used as a template, the degenerate primer pair is adopted for PCR amplification and sequencing; 6, a sequencing result is compared in an existing database to obtain a full-length gene sequence comprising the section most identical with the sequencing result; 7, a primer pair is designed according to the full-length gene sequence; 8, the genomic DNA of the bacterium to be detected is used as the template, the primer pair is adopted for PCR amplification and sequencing. The method is fast and accurate and has high practical value.