Enzymes are characterized by many advantages, including being needed only in micro-amounts, highly efficient, environmentally friendly and nontoxic, energy saving, highly specific, and able to react under mild conditions. Based on the reactions between enzymes and their specific substrates in milk, desirable results can be obtained safely and efficiently to improve the quality of dairy products. Thus, enzymes are widely used in dairy products. This article reviews the mechanisms of action of lactase, transglutaminase, rennet and lactoperoxidase and their applications in dairy processing and preservation, together with the application of enzyme-linked immunoassay to detect in the detection of dairy products. The aim of this review is to provide a theoretical basis for the application of enzymes in the processing, preservation and detection of dairy products.