HCl emission characteristics during the combustion of eucalyptus bark were carried out at various temperatures. The influence of the various additives on the HCl emission was investigated by the experiment, Fact Sage, and X-ray diffraction. The results showed that the HCl emission could be divided into two stages at 500 degrees C. The totality of the HCl emission at 500 degrees C was an order of magnitude higher than that at 600 degrees C. The peak value of the HCl emission curves increased initially and then decreased with the temperature between 500 and 900 degrees C, while the totality of the HCl emission decreased with the temperature. Calcium oxide and aluminum oxide could reduce the HCl emission during the combustion process. However, the removal effect of the HCl emission decreased with increasing the temperature. Unlike calcium oxide and aluminum oxide, the addition of kaolin to the bark could increase the HCl emission. The deviation between the simulation and practical results increased at a low temperature. Moreover, all of the additives could retain potassium in the residue of the eucalyptus bark, but the effect of kaolin to retain potassium was more significant than the effect of the other additives.