A three-way catalytic control method for reducing fuel consumption is provided. The method includes determining whether oxygen storage capacity of the three-way catalyst is under condition of increasing oxygen, when condition of performing O2 purge control for the three-way catalyst is detected and performing O2 purge control by applying a predetermined O2 purge time period to which a set initial value of oxygen of OSC is applied, when the OSC is not under the condition of increasing oxygen. The O2 purge control is performed by applying O2 purge time period for a deteriorated product based on an oxygen sensor or O2 purge time period for on board diagnosis, when an increase amount of the calculated O2 purge time period is equal to or greater than the O2 purge time period for the deteriorated product during the O2 purge control.