To study the effects of triterpenoid components from Prunella asiatica on phase II detoxifying enzymes and protein expression in vitro and in vivo. Normal human bronchial epithelial (NHBE) cell model was used in vitro, and the mouse model of Kunming (KM) mice was used in vivo. CDNB assay was used to measure the activity of GST. NADPH and DCIP was used to detect the activity of NQO1. DTNB colorimetric assay was used to detect GSH. Western blot was use to detect the protein expression of NQO1. We found that triterpenoid components from P. asiatica could increase the activity of GST, NQO1 and GSH in NHBE cells and KM mice. NQO1 protein expression can also be increased in vitro. The study suggests that triterpenoid components from P. asiatica can prevent the lung cancer by regulating the body phase II detoxification enzyme activity and protein expression.