Abstract: OBJECTIVE To study the effect of serum thyroid hormone and body temperature before and after Coptidis Rhizoma processed with the pig’s bile on the febrile rats. METHODS A febrile type model was established with Aconitum carmichaeli Debx., Zingiber officinale Rosc. and Cinnamomum cassia Presl. decoction in rats, and then were given an injection of dry yeast subcutaneously to produce and release pyrogen, and the body temperature of adjusting point was raised up, so the febrile model was established successfully. The febrile model rats were administrated with Coptidis Rhizoma, pig’s bile and the bile processed Coptidis Rhizoma, respectively. Recording the body temperature of every rat, blood sample were drawn for detection of serum FT3, FT4 and rT3. RESULTS Compared with the normal group, the model group had significantly higher levels of body temperature(P<0.001), but lower levels of serum FT3, FT4 and rT3(P<0.01). Compared with the model group, the body temperature after 3 h decreased significantly(P<0.01) in the pig’s bile group and the bile processed Coptidis Rhizoma group. Coptidis Rhizoma and the bile processed Coptidis Rhizoma could significantly increase the level of FT3(P<0.05), the pig’s bile could significantly reduce the level of FT4(P<0.05), there was no significantly difference on rT3. CONCLUSION The pig’s bile and the bile processed Coptidis Rhizoma can antagonize the increase of the body temperature of rats. Coptidis Rhizoma and the bile processed Coptidis Rhizoma can improve metabolism in febrile rats by antagonizing the decrease of FT3 levels.