Pear vinegar was produced from ripe peaches by liquid-state fermentation and changes in biochemical parameters were monitored during the “two-step” fermentation process. “Skin-on” fermentation was carried out after pulping and inoculation with 0.05% wine yeast. Fermentation lasted for 80 h at a constant temperature of 20 ℃, with an alcoholic content of 6.07% (V/V). Acetic fermentation was carried out in a self-priming, submerged fermentation tank after inoculation with 10% acetic acid bacteria. Acetification lasted for 60 h at 34 ℃ with titratable acidity of 3.54% (m/V). Nine organic acids were found in the peach wine fermentation liquor, including oxalic acid, formic acid, malic acid, α-ketoglutaric acid, lactic acid, acetic acid, citric acid, fumaric acid, and succinic acid. The organic acid content was constantly changing during fermentation, which significantly contributed to the acidity and quality of the fermentation liquor. During alcoholic fermentation, lactic acid was produced and accumulated, while the concentration of malic acid and citric acid decreased significantly. Acetic acid bacteria transformed alcohol to acetic acid, the concentration of which increased significantly, while the concentration of the majority of the remaining organic acids, such as lactic acid and malic acid, decreased during acetification. Thus, the “two-step” fermentation method used in this study is suitable for the production of peach vinegar.