Method of controlling exhaust gas purification system, and exhaust gas prufication system

A method (1) of controlling an exhaust gas purification system has a DPF device (12), where a regeneration control means (35C) has a forced regeneration mode and an arbitrary regeneration mode. In the forced regeneration mode, when it is determined by a regeneration time determination means (34C) that it is time to regenerate a filter (12b) and the temperature of exhaust gas is low, the exhaust gas temperature is raised by an exhaust gas temperature raising means (351C) to forcibly regenerate the filter (12b). In the arbitrary regeneration mode, the filter is arbitrary regenerated based on the result of detection by a collection amount detection means (32C). While the temperature of exhaust gas is raised in the arbitrary regeneration mode by the exhaust gas temperature raising means (351C), operation of a compressor (41) of a vehicle air conditioner is stopped. By means of this, the temperature (Tw) of engine (10) coolant is prevented from abnormally rising while the DPF device (12) is forcibly recovered by arbitrary regeneration.