Abstract: In processing of quickdissolve soyamilk the concentrating technique can remove 60 ％～70％ moisture in the soyamilk． A technique of vacuum concentration for the soyamilk was discussed to improve the efficiency of drying． The main parameters affected the viscosity in concentrating were discussed， such as the vacuum Z₁, the steam pressure Z₂, and the soyabean milk density Z₃. The correlation equation of the viscosity of soyabean milk and the parameters were established by an orthogonal quadratic regression rotary combination test. The effects of the parameters on the viscosity of soyabean milk were developed by the significant and relative analysis. The optimal parameters to make the viscosity of soyabean milk minimum were determined: Z₁=0.087MPa, Z₂=0.147MPa/cm², Z₃=20 %.