In order to study the volatile flavor of soymilk, a soymilk simulation system with soybean oil body as substrate was constructed, The effects of different pH on the components, particle size and flavor of soybean oil body extracted from soybean milk were studied in the oil body extraction process. The results showed that when the extraction pH increased from 7 to 11, the content of oil body protein decreased by 38.40%, the neutral fat content increased by 7.26%, and the phospholipid content decreased by 49.31%. The oil particle size decreased gradually by 89.2 nm and tended to be stable. Volatile flavor substances were also gradually reduced from 129.80 μg/L to 52.17 μg/L. When the pH > 9, the effect of lipoxygenase in extracted oil body was negligible. According to the comparison above, the purity and stability of oil body extracted under the condition of pH 10 were better, and the flavor substances contained in the oil body were also less. It can be seen that the oil body extracted at pH 10 is the most suitable substrate component of soybean milk simulation system.