A method for controlling an exhaust gas purification apparatus including a front three-way catalyst (TWC) and a rear TWC that purify the exhaust gas may include determining an oxygen flow rate and a flow rate of a reducing agent introduced into the front TWC, determining the oxygen storage amount of the front TWC based on the oxygen flow rate and the flow rate of the reducing agent flowing into the front TWC, determining a maximum oxygen storage amount of the front TWC, determining a slip oxygen flow rate and a slip reducing agent flow rate of the front TWC, determining an oxygen storage amount of the rear TWC, comparing a rear TWC oxygen storage amount and a target value of the rear TWC oxygen storage amount, and maintaining a catalyst purge of the front TWC when the rear TWC oxygen storage amount is greater than the target value of the rear TWC oxygen storage amount.