Preparation method of tetrandrine

The invention relates to a medical technology, in particular to a tetrandrine preparation method. According to the method, the tetrandrine A and the tetrandrine B are extracted from the stephania tetrandra powder by utilizing an ultrafiltration membrane, and then the high-quality tetrandrine B with the purity of 99.5% or above and the maximum single impurity of 0.05% or below is obtained through the procedures of solvent purification, refining and the like. 本发明涉及医药技术，具体涉及汉防己乙素制备方法。本发明利用超滤膜先从汉防己粉中提取出汉防己甲素和乙素，再通过溶剂纯化和精制等工序，得到纯度99.5％以上，最大单杂0.05％以下的高质量汉防己乙素。