The present invention provides a method of determination of the driving mode of a hybrid vehicle. The method is executed by a hybrid control unit (HCU) and includes the step of modeling a PNGV (Partnership for a New Generation of Vehicles) systems analysis toolkit (PSAT) to calculate power reserved to drive a motor. Thereafter, whether or not the driving mode of the hybrid vehicle is consistent with an electric vehicle (EV) mode is determined using the power reserved to drive the motor, which has been calculated using the PSAT model. If the driving mode is not consistent with the EV mode, whether or not the driving mode is consistent with a maximum (MAX) torque mode is determined. If the driving mode is not consistent with the MAX torque mode, the driving mode is determined to be a hybrid-electric vehicle (HEV) mode.