In this study, Lactobacillus plantarum was used as a partial substitute for sodium salt to produce salt-reduced, umami-enhanced dry-cured mackerel. Through sensory evaluation and comparative analysis of taste substances, it was found that the salty, umami and kokumi taste of the product with a substitution level of 50% was significantly better than that of control groups 1 (with 4% sodium salt) and 2 (with 2% sodium salt) (P < 0.05), indicating that L. plantarum could produce a large amount of umami and kokumi substances as well as salty substances or salty-enhancing substances to replace sodium salt. Moreover, the proportions of umami amino acids and taste-active peptides with molecular mass less than 1 kDa in the sample with L. plantarum were significantly higher than those in the control groups (P < 0.05). These substances could not only have umami and kokumi taste, but also enhance salty taste. In addition, the water activity and pH were significantly lower than those of the control groups (P < 0.05), which could be beneficial for the preservation of dry-cured mackerel, but there was no significant difference in color difference when compared to the control groups (P > 0.05), indicating that the appearance quality of the product was not affected by L. plantarum. The results showed that the addition of L. plantarum could not only reduce the addition of sodium salt in dry-cured mackerel, but also increase its umami and kokumi taste.