Radix Ranunculi Ternati the dried root tuber of Ranunculus ternatus Thunb. is neutral, sweet, pungent and warm, and enters the liver and lung meridians. It has the effects of removing toxicity, resolving phlegm and dissipating nodulation. We undertook this work to study the effect of extracted polysaccharides from Radix Ranunculi Ternati on Type I skin hypersensitivity. Water extraction and ethanol precipitation was used in extraction. Phenol-sulfuric acid method was used in determination of polysaccharides and type I hypersensitivity was established in rats. The rats were randomized into the blank control group, chlorphenamine group, cortisone group and Radix Ranunculi Ternati polysaccharide low-, medium- and high-dose groups (0.50, 1.00 and 1.50 g/kg). Polysaccharide content in Radix Ranunculi Ternati extract was determined to be 6.7%; the three doses could significantly inhibit the diameter of antiserum-induced blue reaction spots on dorsal skin of rats (P<0.01), of which the high- and medium-doses had efficacies equivalent to chlorpheniramine. Three Radix Ranunculi Ternati polysaccharide dose groups could inhibit histamine- and serotonin-induced increase in capillary permeability in rats, and inhibit histamine- induced paw edema in rats (P<0.01), of which the efficacies of high- and medium-dose groups were not significantly different from the chlorpheniramine group. Hence, polysaccharides from Radix Ranunculi Ternati may suppress type I skin hypersensitivity by the pathway of anti-allergic inflammatory mediators.