The present invention discloses Planococcus and a method for improving fermentation quality of a low-salt fish sauce by Planococcus, and relates to the application field of food microbiology technology. The Planococcus strains have been deposited in China General Microbiological Culture Collection Center (CGMCC) under CGMCC NO. 17057, CGMCC NO. 17058, CGMCC NO. 17059, and CGMCC NO. 17060. The production cycle of fermented fish sauce using the Planococcus strains is greatly shortened, and the fermentation temperature is reduced. The fish sauce obtained by this method is transparent brown red, and has the unique aroma of aquatic products without impurities such as suspension or flocculent. The finished fish sauce has low salt content and high amino acid nitrogen content (according to the Chinese fish sauce industry standard, the fish sauce is classified as first-grade fish sauce). The contents of total volatile basic nitrogen and histamine are lower than the national standard.