PURPOSE: To obtain a proper dry treatment method for removing acid gas, heavy metals, and dioxins in exhaust gas.

CONSTITUTION: The following processes are set up: in the first process, high temperature combustion exhaust gas is led to the first bag filter 1, calcium hydroxide powder and a reaction auxiliary are added into the gas, the concentrations of HCl, SOx, and dust in the gas are decreased so that the gas can pass through an ammonia-reduction selective denitration catalyst in the next process, and part of heavy metals and dioxins are removed; in the second process, the high temperature exhaust gas treated in the first process is led to an ammonia-reduction selective denitration catalyst apparatus, and ammonia is added into the gas to remove NOx; in the third process, the exhaust gas, which was treated in the second process and is still hot, is introduced into a cooler 3, and water or calcium hydroxide slurry is supplied to cool the gas; in the fourth process, the exhaust gas cooled in the third process is led to the second bag filter 4, and calcium hydroxide powder and a reaction auxiliary are added into the gas, and residual HCl, SOx, heavy metals, dioxins, and dust are removed.