Abstract: Abstract: China is a big agricultural country, and soybean production ranks the forefront of the world. Soybean is a high quality nutrient source, and the main nutrient in soybean is soybean protein with the content of about 40%. Soybean protein powder is the soybean meal after oil extraction, which can improve the utilization of soybeans and the economic value to a large extent. Besides, soybean oil is rich in unsaturated fatty acids, and it can effectively reduce plasma cholesterol, prevent cardiovascular disease, and promote lipid metabolism to prevent subcutaneous fat's accumulation. Extrusion is a high-temperature and short-term treatment process, and most of the anti-nutritional factors are heat-sensitive substances, and thus can be inactivated in high temperature. Extrusion technology has the advantages of high production efficiency, wide applicability of raw materials and improvement of practical quality. The traditional soybean oil process has leaching and pressing methods, but the leaching method causes a certain amount of solvent residue, and the squeezing process rate is relatively low. In order to improve the utilization of soybean meal and meet the requirements of today's soybean production process, in this paper, soybeans were used as raw material to study the method that uses extrusion machine to process the broken, quenched and washed soybeans, instead of steaming fry and rolling billet process, and then squeezes part of the oil to make the extruded soybean protein powder. The effects of water content, extrusion temperature, screw speed and pore aperture on the urease activity of soybeans were studied by single factor and response surface optimization. The results showed that the urease activity of soybean meal was 0.021 U/g under the conditions of water content 9.0%, extrusion temperature 160 ℃, screw speed 270 r/min, and pore aperture 18 mm. The method of response surface analysis was used to optimize the soybean extrusion technology parameters, and the extruded soybean protein powder was prepared according to the optimized process parameters. Extruded soybean protein powder is usually used as animal feed. Compared with the defatted protein powder, it is more in line with the requirements of the aquaculture industry feed, and the method reduces the step of adding fat to the feed, simplifies the feed processing process, and effectively reduces the cost of production; protein powder containing oil has a better stability and is not easy to rancidity. In addition, the effect of extrusion was observed by transmission electron microscopy, and according to the results, the fat in soybean was exposed. Finally, the indices of extruded soybean protein powder prepared by extrusion and traditional oil extraction method were measured. The results show that the product of extruded soybean protein powder has a fat content of 7.1%, and NSI (nitrogen solubility index) value of 80.5%, and the extrusion process can be applied to the processing of feed. In this experiment, the original soybean oil pressing process is improved, the soybean extrusion step is increased, and the soybean meal after crushing can be made into extruded soybean protein powder, which reduces the step of adding oil, reduces production costs, improves the utilization of soybeans, and extends the industrial chain.