Abstract: Soluble dietary fiber has small molecular weight, disordered structure and good physicochemical properties. However, natural dietary fiber possesses low bioavailability due to the low content of soluble dietary fiber, so it is essential to modify it. Traditional modification methods such as physical and chemical methods have the disadvantages of high cost, high energy consumption and environmental pollution. Enzymes produced by microorganisms are able to break the glycosidic bond of macromolecules and convert insoluble macromolecules into soluble dietary fiber. Therefore, fermentation is a low-cost, low energy consumption, green and pollution-free new modification method. This article systematically explains the principle of fermentation modification and the factors that affect the modification effect, such as inoculation amount, temperature, pH and so on, then it introduces the physiological function of dietary fiber by fermentation modification and its application in food products such as flour products, dairy products, meat products, providing theoretical basis for further development and utilization of dietary fiber in the future.