Soluble dietary fiber can inhibit the hydrolysis and digestion of starch, in order to study the effect of inulin on the quality of biscuits, the formula of inulin biscuits was optimized by uniform design method, and the effect of inulin on biscuit digestion was studied by simulating the digestion process of human gastrointestinal tract. The results showed that the best formula was as follows: low-gluten flour 100g, water 20 g, xylitol 15.05 g, inulin 12.60 g, oil (butter: corn oil = 1:1) 31 g, baking soda 0.5 g, salt 0.5 g. In addition, fat content was 16.54%, protein 3.33%, dietary fiber 6.87%, and carbohydrate 56.63%. The results of in vitro digestion showed that the content of the fast-digested starch decreased from 14.51% to 3.06%, and the content of the slow-digested starch and resistant starch increased by 3.67% and 0.20%, respectively. The in vitro digestibility of inulin biscuits was lower than that of blank biscuits, and the inulin biscuit was predicted to have a blood sugar index of 68.36, which is a medium glycemic index food. Therefore, inulin can inhibit the hydrolysis and digestion of starch and reduce the glycemic index of high-fat biscuits. The application of inulin is of great significance for the development of low and medium glycemic index products.