The purpose of this study was to develop a nasal in situ gel system for Radix Bupleuri employing gellan gum as a polymer. Radix Bupleuri in situ gel containing 0.2 mL essential oil extracted from 450 g Radix Bupleuri, proper solubilizing agents and gellan gum (0.5% w/v) was prepared and characterized. The antipyretic effect produced by in situ gel formulation was investigated in fevered rabbits and compared to an intranasal solution. The resulting in situ gel was a clear and light-yellow liquid, with viscosity of 346 $mPa{cdot}s$ and caproic acid content of $1.31{pm}$ 0.01 mg/mL. Intranasal administration of this preparation to fevered rabbits decreased body temperature markedly ($1.1^{circ}C$ at the doses of oil from 1.5 g Bupleuri/body) and the effect could last for 20-30 h. The results suggest that Radix Bupleuri in situ gel can be greater effective than the solution in the treatment of fever.