Abstract: In order to improve the fermentation ability of daptomycin-producing bacterium streptomyces roseolae, by screening sodium caprate resistant strains, optimizing the method of supplementing N-decanoic acid in its fermentation flask, improving the shake flask effect value of tropicolin.The original strain was selected for sodium caprate resistance, a strain TR21-29 with a blank shake flask efficacy value of 43.4 mg·L^-1 was screened out.We took advantage of the strain′s tolerance to caprate, verified the optimal strategy of supplementing N-decanoic acid in its fermentation flask.This study mainly investigated the coupling agent of N-decanoic acid, and feed time, feed concentration and feed interval for adding N-decanoic acid to fermentation flasks, determining the key parameters for the addition of N-decanoic acid to fermentation flasks.The results showed that the original efficacy value of the resistant strain TR21-29 was increased from 43.4 mg·L^-1 to 138.1 mg·L^-1,and the improvement rate was 218.2%.The feeding method is to start adding N-decanoic acid solution after culturing in the fermentation flask for 24 hours.The concentration of N-decanoic acid is 0.5 g·L^-1,the feed final concentration is 1.5 mmol·L^-1,and the feed is fed every 4 hours.