The key hypothesis of this study is that: (1) the efficacy of syndrome differentiation(individualized decoction) will be better than placebo in patients with stable bronchiectasis through N-of-1 trials. (2) the efficacy of syndrome differentiation(individualized decoction) will be better than the same prescription minus heat-clearing Chinese herbs in patients with stable bronchiectasis through N-of-1 trials. The difference of efficacy may be various according to the individual severity of phlegm-heat.