Toutongling Capsule is a Chinese herbal preparation developing from an ancient formula processed by modern technology. Previous clinical studies have shown that Toutongling Capsule exerts a good effect on vascular headache, tonic headache and traumatic headache. To further explore its pharmacological mechanism, the effect of Toutongling Capsule on cerebral vessels and blood viscosity in experimental dogs was observed. The results showed that Toutongling Capsule can decrease cerebral vascular resistance obviously and increase cerebral blood flow, with a good dose-effect relationship. As compared with Yangjiao Granule, Toutongling Capsule possesses a similar effect on blood viscosity but stronger effect on dilatation of cerebral vessels and increase of cerebral blood flow. Both Toutongling Capsule and Yangjiao Granule have no effect on blood pressure and ECG.