An apparatus and method for controlling an electrical stimulation system to increase the resolution of the stimulation region with multiple independent power source electrodes is proposed. In the apparatus, the electrode set contains at least three electrodes of which two adjacent electrodes are of the same power polarity to control the location of the composite stimulation signal and the others are of an inverse power polarity to balance the total power polarity and narrow the stimulation region. The method for the apparatus comprises steps of: receiving a target stimulation location and level, generating at least one parameter to adjust power settings of the electrodes, thereby obtaining a composite stimulation signal corresponding to a virtual channel of which a location and level match the target stimulation location and level.
