Recently, in accordance with the increased interest of consumer in fuel efficiency due to the phenomenon of high oil price, complaints against actual fuel efficiency in the road in comparison with the certified fuel efficiency have been raised frequently. Especially in case of the hybrid vehicle which is highly popular for the reason of its high fuel efficiency compared with that of existing gasoline car, deviation in the fuel efficiency will be higher compared with that of gasoline car in accordance with the driving mode (downtown/highway), driver's driving style (wild/mild) and external environmental condition (gradient/temperature/altitude). To solve them, this paper developed a method so that the SOC (State Of Charge), EV/HEV mode transition point can be controlled variably in accordance with the driving mode, driver's driving style and external environmental condition by making the most of characteristics of hybrid. Through it, efficient engine operating point could be secured even in the driving situation under severe condition while maintaining a stable SOC value, and it was verified that there are effects of increases in the average fuel efficiency and reduction of deviation in the fuel efficiency (about 5.9 mpg, 10∼20%) among vehicles through HILS (Hardware-In-the-Loop-Simulation) validation. Application of this developed logic to 12 MY YF/TF hybrid vehicles of HYUNDAI MOTORS has been completed.