The aim of this study was to investigate the influence of brine concentration on certain physicochemical properties and microbial community characteristics in naturally fermented mustard greens pickles from the Chaoshan region. During the fermentation stage after pre-pickling, the salt concentration of the brine was adjusted to create gradients of 3 wt.%, 4 wt.%, and 5 wt.%. Throughout fermentation, changes in brine salinity, total acidity, appearance and flavor, reducing sugar, amino acid nitrogen, total lactic acid bacteria count, and total colony count were measured, and high-throughput sequencing of the bacterial community on the pickles was performed at the end of fermentation. The results indicated that salt concentration significantly affected both physicochemical properties and microbial populations during fermentation. After 10 days of fermentation, the total acid content differed by 1.83 g.kg-1 between pickles fermented at 3 wt.% and 5 wt.% salt; the time to peak reducing sugar content differed by 3 days between these two concentrations, whereas the difference between 3 wt.% and 4 wt.% was 1.06 g.kg-1. Brine at 3 wt.% resulted in a higher proportion of spoilage and pathogenic bacteria, whereas brine at 5 wt.% partially inhibited the growth of non-halotolerant lactic acid bacteria, resulting in a lower proportion of lactobacilli (21%). Moreover, a lower salt concentration appeared to accelerate the fermentation process. Based on microbial composition and amino acid nitrogen content, brine with 4 wt.% salt was determined to be the most suitable for fermenting Chaoshan mustard greens pickles after pre-pickling. This study provides a theoretical basis for understanding the fermentation process of naturally fermented mustard greens pickles from the Chaoshan region and for selecting the appropriate salt concentration for preparing such pickles.