The roles of many sigma factors are unclear in regulatory mechanism of secondary metabolism in Streptomyces. Here, we report the regulation network of a group 3 sigma factor, WhiG(ch), from a natamycin industrial strain Streptomyces chattanoogensis L10. WhiG(ch) regulates the growth and morphological differentiation of S. chattanoogensis L10. The whiG (ch) deletion mutant decreased natamycin production by about 30 % and delayed natamycin production more than 24 h by delaying the growth. Overexpression of the whiG (ch) gene increased natamycin production in large scale production medium by about 26 %. WhiG(ch) upregulated the transcription of natamycin biosynthetic gene cluster and inhibited the expression of migrastatin and jadomycin analog biosynthetic polyketide synthase genes. WhiG(ch) positively regulated natamycin biosynthetic gene cluster by directly binding to the promoters of scnC and scnD, which were involved in natamycin biosynthesis, and these binding sites adjacent to translation start codon were determined. Thus, this paper further elucidates the high natamycin yield mechanisms of industrial strains and demonstrates that a valuable improvement in the yield of the target metabolites can be achieved through manipulating the transcription regulators.