Juice concentrates were rarely served as fermentation substrates. In this work, we utilized comparative transcriptomic and metabolomic methods to investigate the effect of pear juice concentrates as fermentation substrates on the metabolic activity and metabolites of S. cerevisiae. Unconcentrated pear juice (UC) and two types of pear juice concentrates, including forward osmosis (FO) and rotary vacuum (RV) concentrates, were fermented with a commercial S. cerevisiaestrain. The results revealed that both before and after fermentation, compared to UC, FO and RV pear juice concentrates exhibited higher contents of organic acids, primarily malic and citric acids, and amino acids, mainly glutamate and aspartate. Yeasts in the juice concentrates exhibited higher energy demands, which were reflected in the activation of the TCA cycle, pyruvate metabolism, glycolysis pathway, and oxidative phosphorylation, leading to accelerated sugar consumption, faster alcohol production, and elevated contents of volatile components. Additionally, several metabolic pathways regarding amino acids and lipids were activated, such as cysteine and methionine metabolism and steroid biosynthesis. These findings provided valuable knowledge for the application and mechanistic research of juice concentrates fermentation.