An exhaust gas treatment method for an internal combustion engine, comprising a collecting step of collecting particulate matter contained in an exhaust gas discharged from the internal combustion engine in a filter, and an active regeneration step of post-injecting a fuel to heat the exhaust gas to a combustion temperature of the particulate matter in a diesel oxidation catalyst, whereby the particulate matter collected in the filter is burned and removed by the heated exhaust gas, the exhaust gas treatment method comprising: a first step of detecting an exhaust gas temperature at an inlet of the filter and determining whether or not a DPF abnormal combustion causing operation, in which the internal combustion engine shifts from a high rotation or high load operating condition to a low rotation, low load operating condition including an idling condition within a set time, has occurred during the active regeneration step; a second step of increasing an exhaust gas flow by performing at least one operation from among fully opening a throttle valve provided in an intake pipe or an exhaust pipe and not reducing a rotation speed during a low load operation to or below a set value when, in the first step, the exhaust gas temperature at the inlet of the filter is determined to equal or exceed the combustion temperature of the particulate matter and the DPF abnormal combustion causing operation is determined to have occurred; and a third step that is performed in parallel with the second step to reduce a combustion speed of the particulate matter by reducing an oxygen concentration of the filter while continuing the post-injection as is, characterized in that an estimated accumulation amount of the particulate matter is determined, wherein each of the first step to the third step is performed when the estimated accumulation amount exceeds a threshold, and wherein an opening control of the throttle valve is resumed and the post-injection is continued when the estimated accumulation amount falls to or below the threshold. a first step of detecting an exhaust gas temperature at an inlet of the filter and determining whether or not a DPF abnormal combustion causing operation, in which the internal combustion engine shifts from a high rotation or high load operating condition to a low rotation, low load operating condition including an idling condition within a set time, has occurred during the active regeneration step; a second step of increasing an exhaust gas flow by performing at least one operation from among fully opening a throttle valve provided in an intake pipe or an exhaust pipe and not reducing a rotation speed during a low load operation to or below a set value when, in the first step, the exhaust gas temperature at the inlet of the filter is determined to equal or exceed the combustion temperature of the particulate matter and the DPF abnormal combustion causing operation is determined to have occurred; and a third step that is performed in parallel with the second step to reduce a combustion speed of the particulate matter by reducing an oxygen concentration of the filter while continuing the post-injection as is, characterized in that an estimated accumulation amount of the particulate matter is determined, wherein each of the first step to the third step is performed when the estimated accumulation amount exceeds a threshold, and wherein an opening control of the throttle valve is resumed and the post-injection is continued when the estimated accumulation amount falls to or below the threshold.