Lactic acid (LA) is a significant byproduct in Baijiu fermentation, with both D(-)-lactic acid (D(-)-LA) and L-lactic acid (L(+)-LA) being present due to the diverse microbial metabolism involved. L(+)-LA, a key industrial raw material, is metabolizable by humans, unlike D(-)-LA. This study aims to isolate microorganisms from fermented grains that preferentially produce L(+)-LA and apply these strains to Baijiu fermentation processes. We analyzed 106 commercially available Baijiu samples, along with fermented grains, yellow water, and Baijiu samples from 10 Baijiu factories, confirming the coexistence of D(-)-LA and L(+)-LA in fermentation products. Notably, a strong correlation was found between L(+)-LA in fermented grains and L-ethyl lactate (L(+)-EL) in Baijiu. Microbial community analysis revealed that Lactobacillus and Bacillus were the dominant bacterial groups, with a succession of microbial communities throughout fermentation. Two strains, A6 and B12, identified as Bacillus licheniformis and Bacillus cereus, respectively, were isolated for their high selectivity in L(+)-LA production. Both strains demonstrated a high yield of L(+)-LA in fermentation tests. Incorporating these strains into both liquid- and solid-state fermentation systems markedly increased the proportion of L(+)-EL relative to total ethyl lactate in Baijiu. This study successfully isolated and applied L(+)-LA-producing strains to fermentation models, offering a practical strategy for increasing L(+)-LA content in Baijiu.