Egounletyet al.7observed soaking the soybean for 12to 14 hours reduced about 25% raffinose and 20%stachyose, the loss of sucrose in soaking liquids was evenmore than that of raffinose when during the prepartion oftempeh. Prinyawiwatkulet al.25 reported when soakingcowpea in 1: 6 water (cowpea: water, w/w) at 25℃for 24hours the sucrose and stachyose decreased by 39% and18.4% respectively. Ruiz-Terán et al.17found that whenthe soybeans were hydrated in water at 100℃for 30 minthe oligosaccharides losses in the hydration water was 45g/kg initial dry soybean. Different results in oligosaccharides content detected insoaking water might be attributed to different varieties,23,26volume of soaked water, soaking temperature and soakingtime.7,25Soaking is an important operation during the prepara-tion of soybean sheet. Soaking can make the dry beansabsorb a certain volume of water, which facilitated thefollowing grinding process. Li13believed soaking madethe seed soft, the seed structure loose, the protein easilyextracted, the seed components diffuse into water. Thiscontributes to the detectable sugar in the soaked water. Washing the soaked soybeans in water could flow awaythe foam and ash in the soaked soybeans, which is anusual practice in soybean sheet processing. Ruiz-Teránetal.17 reported in their study that washing the soaked soy-beans at 60℃reduced the oligosaccharides content dur-ing preparation of tempeh. Egounletyet al.7reported thecombined effect of soaking, dehulling, washing and cook-ing reduced more than half of oligosaccharides in prepara-tion of bean tempeh. Grinding method might influence the oligosaccharidesconcentration in soymilk. Lasekan et al.27reported that bya fine milling the sugar content in two sorghum cultivarswould be increased. Filtrating separated non-soluble soybean residue fromsoymilk which guaranteed the good quality of soybeansheet. A certain amount of oligosaccharides was left inthe soy residue. Inevitably this lead to certain loss ofoligosaccharides.In the sheet formation process, as water evaporateswith time dry matter in the soymilk increased and the filmthickness as well as the weight of the soybean sheet in-creased too. This was the major reason accounting for theincreasing tendency in oligosaccharides content in finalsoybean sheets recovered later in the process (Figure 4).The results from the present study indicate that soybeanoligosaccharides are easily subjected to loss with varioustreatments, including soaking, grinding, filtrating, boilingwhile the last step of sheet formation accounted for thehighest loss. The by-product in soybean sheet production, the sweetslurry which contains large amount of oligosaccharides,are isnot fully utilized. The analysis of loss profile im-plies possible ways to improve technology for productionof oligosaccharides enriched soy-sheets, and whilstarouses attention to make full use of the by-products inthe processing of the soybean sheet.