Objective : To investigate and compare the antipyretic effect of different processed rhubarb products as well as the mechanism of their antipyretic effect. Method : SD rats were given subcutaneous injection of dry yeast and treated with the processed rhubarb products an hour later. And then anal temperatures of the rats were measured at the 1st, 2nd, 4th and 6th hour,respectively. Radioimmunoassay was adopted to detect the level of cyclic adenosine monophosphate(cAMP) in the hypothalamus of rats. Result : All the processed rhubarb products could lower the rised body temperature to a certain degree and the effect duration could last more than 4 hours. Regarding the effects of all the processed products, the wine-cooked and crude rhubarb showed stronger action than the other two processed products of rhubarb. The correlation analysis further showed that content of cAMP in hypothalamus was positively correlated with the change of body temperature of rats. Conclusion : All the processed rhubarb products have antipyretic effects and their antipyretic mechanisms may be associated with lowering the increased content of cAMP in hypothalamus.