Abstract: OBJECTIVE To explore into the microscopic behavior of different combinations of water extract of Huanglian Jiedu Decoction in the separation process using. METHOD The pH value, conductivity rate, turbidity, viscosity, etc. of the water extract of different drug combination were determined before and after the separation was made. RESULT Different changes occurred in pH value, conductivity rate, turbidity, viscosity, etc. with different drug combination. CONCLUSION PS membrane at molecular weight of ten thousand can change the physical and chemical parameters of different combinations of Chinese drugs in compound recipes.