Reverse transcription quantitative PCR （RT-qPCR） combined with the published genome information of Saccharopolyspora spinosa can allow sophisticated studies about S. spinosa, including Studying the regulation of spinosyn biosynthesis, finding new target genes for engineering, and discovering and exploiting other macrolide secondary metabolites. Studies have demonstrated that appropriate internal control is needed to normalize target genes at transcription levels. However, many studies have shown that no single reference gene is universal for all strains under all experimental conditions. Thus, eight candidate reference genes of three different S. spinosa strains in two different cultures were studied to find suitable reference gene（sl. The number of amplification cycles of these candidate genes was calculated by BestKeeper, NormFinder and geNorm. The results indicated that the most suitable reference genes for normalization during the fermentation of S. spinosa were 16S rRNA and rbL13.
