Caesalpinia Sappan L. that had immunosuppressive function was investigated in this paper. On the basis of establishing the method of determining content of hydroxybenzene in Caesalpinia Sappan L., extractive technology was investigated by orthogonal design. Permeation, soxhlet and ultrasonic extraction were surveyed with water, thirty-five, sixty-five and ninety-five percent of ethanol as solvents. The immuneological functions of watery extract, sixty-five and ninety-five percent of ethanol extracts of Caes...