Abstract: In order to solve the problems of bad taste and inconvenient eating of brown rice, this paper used japonica brown rice and early indica rice as raw materials. Instant brown rice porridge was prepared by twin-screw extrusion and high-temperature drying. Because brown rice is a kind of rice grain with only the shell removed and not polished. It retains most of the rice bran layer, germ, and endosperm. It has high nutritional value. However, because the bran layer of brown rice contains bran wax, phytate, and high fiber, brown rice has some problems, such as compact texture, difficulty in cooking, and rough feeling. During the preparation of instant brown rice porridge, seven factors affect the sensory score and rehydration time of the porridge. They are: screw speed, dying temperature, water content, dosage of compound improver, ratio of starch to starch, drying temperature, and drying time. In this paper, the sensory score and rehydration time of instant porridge were optimized by a single factor experiment. On the basis of this experiment, seven factors affecting sensory score and rehydration time of instant brown rice porridge were studied and optimized through Plackett-Burman experimental design in a factorial experiment. Plackett-Burman experimental design is a factorial experiment, which can help to screen out the factors that have a significant influence on the target value from a variety of single factors. Through Plackett-Burman experimental design in the factorial experiment, four factors (starch ratio/branch ratio, compound improver dosage, material water content, and drying temperature) that have a significant influence on the sensory score and rehydration time of instant steamed brown rice were selected from seven factors that affect instant brown rice porridge and then further optimized by the response surface Box-Behnken design. The optimum preparation conditions of instant brown rice porridge were as follows: amylose amylopectin ratio was 0.26, the amount of compound improver was 0.65%, the water content of the material was 35.4%, and the drying temperature was 165°C. Under this condition of instant porridge, the sensory score of the porridge was 94, and the rehydration time was 5.3 min. And the structural characterization of the porridge was analyzed by Differential Scanning Calorimeter (DSC) and Scanning Electron Microscope (SEM). The results showed that compound improver and starch ratio could increase the gelatinization temperature and decrease the enthalpy of the instant brown rice porridge. Increasing the gelatinization temperature of instant brown rice and decreasing the enthalpy change value can make the starch of instant brown rice more stable and easier to gelatinize. In addition, adding compound improver and high-temperature drying can promote the formation of a large number of holes in the granules of the porridge. A large number of holes in the granules of instant brown rice porridge can improve the water absorption capacity of the porridge during rehydration brewing. Therefore, the rehydration time of instant brown rice porridge in the brewing process is shortened.