Abstract:Taking the puerarin content--- the chief constituent of Pueraria lobata --- as the index in the mixed decoction of Pueraria lobata etc, we have adopted the method of orthogon al experiment to explore the best decocting conditions for Pueraria lobata. The results shew that a better way to decoct Pueraria lobata is to cut the root into slices of 0.4～0.7cm, and water 12～15 times the weight of the root and decoct for 30 minutes. It makes no big difference whether the root is soaked or not.