Disclosed herein is a pedal simulator for an active brake system. According to an aspect of the present invention, the a pedal simulator for an active brake system, which is installed at a master cylinder to receive a hydraulic pressure corresponding to a driver's pedal force and to provide pedal feeling to the driver, includes a simulator block having an oil hole connected with the master cylinder at an upper portion thereof and having a bore therein to be in communication with the oil hole, a damping housing coupled to seal a lower end of the bore, a first reaction piston provided in the bore to be slidable by oil introduced from the master cylinder, a second reaction piston slidably provided in the bore and disposed under the first reaction piston to be spaced apart from the first reaction piston in a predetermined distance, a first damping member installed at the first reaction piston to be moved together with the first reaction piston, a second damping member installed at the damping housing and configured to provide a reaction force by pressing of the second reaction piston, and a reaction spring provided between the second reaction piston and the damping housing.