Mold spoilage and nutrition enrichment are major concerns of Chinese steamed bread, and using functional lactic acid bacteria as starter to play the role of in-situ preservation and nutritional fortification was a promising alternative. Hence, Lactiplantibacillus plantarum P10 capable of inhibiting spoilage microorganisms and producing γ-aminobutyric acid (GABA) (380 mg/L) was screened from Chinese pickle. Metabolomics analysis showed that P10 produced key antimicrobial metabolites mainly including ten organic acids, aldehyde, alkaloid. Besides, P10 might exhibit health beneficial effects such as degrading cholesterol, lowering blood glucose and reducing uric acid due to the production of deoxycholic acid and Ile-Pro-Ile, and the degradation of purine. Finally, the promising application potential of P10 was evidenced in steamed bread with extended shelf life, excellent anti-aging effect, and 24.5-fold enrichment of GABA. Conclusively, this investigation could provide scientific basis for the application of P10 as a functional starter in steamed bread.