The present invention discloses a potentiometric biosensor for detecting lactate in food, and the forming method thereof. The disclosed biosensor comprises a substrate, and conducting layer on the substrate, an oxide layer on the conducting layer, and an enzyme layer on the oxide layer, wherein the enzyme layer comprises Lactate dehydrogenase (LDH). The detection signal is transmitted for further processing through a wire connected to the conducting layer, or a window formed on the surface of conducting layer.