In order to confirm the soybean protein solution properties and rheological behavior after combined with lecithin, the surface charge, particle size, fluid type and the solution viscosity of lecithin-soybean protein complex were investigated. The results showed that the enhanced negative charge of protein particle, greater particle size and improvement of soluble protein were occurred with the increasing of combined lecithin content. The rheological characterization data displayed that the corresponding protein concentration reduced gradually when the n value, which indicated the fluid type, began to less than 1 with the increasing of lecithin combined content. This change explained that the complex of lecithin on soybean protein could lower the inflection point of protein concentration which indicated the change of fluid type. And then the protein viscosity was reduced by the effect of moderate lecithin content. 