This brief proposes a synergetic excitation control strategy for a seven dimensional chaotic power system. Firstly, chaotic phenomenon in the complex power system is analyzed. Then, a new macro variable expression is constructed for the power system and the excitation controller design process is carried out. In order to compare the proposed excitation control with traditional control method, the excitation controller is also designed under the traditional macro variable definition. Finally, simulation results show that the proposed excitation control method can not only effectively suppress chaotic oscillation in the power system, but also can improve bad transient phenomenon and overcome the difficulty of parameter selection in the traditional method, so that it has advantages in control performance and reducing difficulty for project implementation.