Abstract: In a continuous foam fractionation column, the effects of various operation conditions, such as protein concentration, gas flow rate, pH, reflux ratio, ratio of foam height to liquid pool height etc. on separation of soybean protein were investigated. The optimum operation conditions were then obtained. Furthermore, surface excess concentration of soybean protein at gas liquid interface was measured by fluid method. The results indicated that surface excess concentration was linear to solution concentration at low concentrations Linear isothermal adsorption equation was given.