Objective: To identify the influence of extracts and active components of Rhizoma Coptidis on gastric smooth muscle contractility of guinea pigs, and to explore the potential pharmacological mechanism of Rhizoma Coptidis in "invigorating the stomach" and "impairing the stomach". Methods: Observing the effects of the water extract and the alkaloids from Rhizoma Coptidis (at doses ranging from 0.3 to 1 000 mug/L) and other active components such as berberine, palmatine and jatrorrhizine (at doses ranging from 0.3 to 1 000 mumol/L) on the spontaneous and electrical field stimulation (EFS)-induced contractions of antral circular smooth muscle strips from guinea pig stomach via a force transducer in vitro. Results: The water extract or the alkaloids from Rhizoma Coptidis could improve the spontaneous contraction at the low doses, but inhibit the spontaneous contraction at the high doses. Berberine, palmatine and jatrorrhizine also showed the similar effects. Moreover, the water extract and the alkaloids of Rhizoma Coptidis, as well as berberine, palmatine and jatrorrhizine could increase the EFS-induced contraction. Among the three monomers, jatrorrhizine exhibited the most potent effect on EFS-induced contraction. Conclusion: The effects of Rhizoma Coptidis in "invigorating the stomach" or "impairing the stomach" may be related to its effect on gastric smooth muscle contractility. Berberine, palmatine and jatrorrhizine are all effective components of Rhizoma Coptidis affecting the contraction of gastric smooth muscle, among which jatrorrhizine is the most potent agent in promoting the contraction while berberine is the most potent one for inhibiting the contraction.