As a clinical symptom, cognitive impairment belongs to vascular cognitive impairment (VCI) or Alzheimers Disease (AD). Traditional Chinese Medicine(TCM) regards that “brain and marrow insufficiency” is the root cause and “collateral obstruction by phlegm” is the manifestation for dementia. Recent studies regard that “brain collateral damage due to toxin” is the mechanism of dementia. TCM believes that Rhubarb can tonify the body by removing stasis, and can relax bowels and reduce turbid, activate blood and remove stasis, and clear heat and expel toxin, and thus to be used in treating dementia. Recent pharmacology studies suggest that Rhubarb excel in antioxidant and anti-aging, which can be used to improve the cognitive function of elder people. Also, studies on Rhubarbs function to clear turbid in intestine showed that it can remove stasis and promote regeneration, especially eliminate enterogenous endotoxin. Consequently, it can contribute to the improvement of cognitive function.