The definition of dietary fiber （DF） includes multiple meanings involving material structure，physiological and biological effects. So， to accurate evaluate DF level in foods，it’s necessary to grasp scientific concepts and rigorous measurement techniques. Now， the new version of the National Food Safety Standard Determination of Dietary Fiber in Foods （GB 5009.88—2023） has been implemented in China. Compared to pre-version， high-performance liquid chromatography technique is added in enzymatic-gravimetric methods， making it possible to include insoluble and soluble dietary fiber， even that cannot be precipitated by 78% ethanol， in total dietary fiber results， and the detection scope is expanded. For better understanding the method to use， this article summaries the relation of determination methods to definition development， interprets in details about the principles， determination pathway and steps， and result expression. Simultaneously， the application scope of the method and its connection with other national standards has also been discussed.