Backgrounds: Roflumilast is an oral inhibitor of phosphodiesterase 4(PDE4), which is mainly metabolized by CYP3A4 and CYP1A2.The main metabolite of it is roflumilast N-oxide, which contributes to the efficacy largely.While it has been proved that the abundance of CYP1A2 demonstrated a significant difference between Chinese and Caucasian, which may lead to a significant difference of exposure between Chinese and Caucasian.In addition, it has been shown a very difference adverse event (AE) profile of roflumilast among Chinese COPD patients from that among Caucasian COPD patients.Objects: This essay is aimed to predict AE probabilities and appropriate dose of roflumilast for Chinese COPD patients based on physiologically-based pharmacokinetic (PBPK) model and population pharmacokinetic (PopPK) models.