Plant adventitious root culture in bioreactors is a promising alternative for the efficient production of medicinal herbs. Adventitious roots of Pseudostellaria heterophylla were induced from callus and then cultivated in a siphon-mist bioreactor. An orthogonal test established that the optimal medium for adventitious root induction was MS medium supplemented with 1.0 mg/L naphthaleneacetic acid and 2.0 mg/L 3-indolybutyric acid. Under these conditions, the average root number was more than 14 on each 1.0 cm diameter callus and the rooting rate reached 100%. The bioreactor was equipped with an integral siphon-spraying device designed to automatically supply the liquid medium. The operation parameters of the bioreactor were assessed by varying the mist interval and the aeration velocity. The mist interval was negatively related to average growth rate of the adventitious roots and positively related to saponin and polysaccharide content. A relatively high aeration rate was necessary to achieve the maximum biomass production, but the secondary metabolite production was not enhanced by increasing the aeration velocity.