A method of controlling an exhaust gas purification system, the system provided with an exhaust gas purification device, having an oxidation catalyst device supporting an oxidation catalyst and a diesel particulate filter device disposed, in that order, from the upstream side of an exhaust gas passage in an internal combustion engine, or an exhaust gas purification device provided with a diesel particulate filter device supporting an oxidation catalyst, index temperature detecting means for detecting a catalyst temperature index temperature that indicates the temperature of the oxidation catalyst, and a control device that conducts a forced regeneration control for recovering the purification ability of the diesel particulate filter device based on the detection results of the index temperature detecting means, the control device conducting, during forced regeneration control, a first exhaust gas temperature raising control when the catalyst temperature index temperature is lower than a predefined first judgment temperature, the first exhaust gas temperature raising control involving multi-injection without post-injection as part of an in-cylinder fuel injection control, and conducting, during forced regeneration control, a second exhaust gas temperature raising control when the catalyst temperature index temperature is equal to or greater than the predefined first judgment temperature, the second exhaust gas temperature raising control involving post-injection conducted in addition to multi-injection as part of an in-cylinder fuel injection control, characterized in that, the method comprises: calculating injection quantities and injection timings for the multi-injection conducted in the first exhaust gas temperature raising control based on map data for the first multi-injection; calculating injection quantities and injection timings for the multi-injection conducted in the second exhaust gas temperature raising control based on map data for the second multi-injection; and the map data for the second multi-injection is different from the map data for the first multi-injection, wherein in the first exhaust gas temperature raising control, the injection quantities for the multi-injection are increased, and the injection timings for the multi-injection are delayed to be later than the fuel injection timings for ordinary operation; and in the second exhaust gas temperature raising control, the injection quantities for the multi-injection are reduced to the quantity necessary for maintaining the exhaust gas temperature of the exhaust gas entering the particulate filter, and the delay in the injection timings for the multi-injection is reduced to less than that of the injection timings for the multi-injection in the first exhaust gas temperature raising control. conducting, during forced regeneration control, a first exhaust gas temperature raising control when the catalyst temperature index temperature is lower than a predefined first judgment temperature, the first exhaust gas temperature raising control involving multi-injection without post-injection as part of an in-cylinder fuel injection control, and conducting, during forced regeneration control, a second exhaust gas temperature raising control when the catalyst temperature index temperature is equal to or greater than the predefined first judgment temperature, the second exhaust gas temperature raising control involving post-injection conducted in addition to multi-injection as part of an in-cylinder fuel injection control, calculating injection quantities and injection timings for the multi-injection conducted in the first exhaust gas temperature raising control based on map data for the first multi-injection; calculating injection quantities and injection timings for the multi-injection conducted in the second exhaust gas temperature raising control based on map data for the second multi-injection; and the map data for the second multi-injection is different from the map data for the first multi-injection, wherein in the first exhaust gas temperature raising control, the injection quantities for the multi-injection are increased, and the injection timings for the multi-injection are delayed to be later than the fuel injection timings for ordinary operation; and in the second exhaust gas temperature raising control, the injection quantities for the multi-injection are reduced to the quantity necessary for maintaining the exhaust gas temperature of the exhaust gas entering the particulate filter, and the delay in the injection timings for the multi-injection is reduced to less than that of the injection timings for the multi-injection in the first exhaust gas temperature raising control.