Disclosed herein is a pedal simulator for an active brake system. The pedal simulator includes a simulator block provided therein with a bore, a first reaction unit including a first reaction piston slidably installed in the bore, a first damping member installed at the first reaction piston, and a first reaction spring compressed by the first reaction piston, and a second reaction unit including a second reaction piston provided in the bore to support the first reaction spring and slide in the bore, a damping housing connected to the simulator block to be spaced a certain distance apart from the second reaction piston, a second reaction spring installed between the second reaction piston and the damping housing to be compressed by the second reaction piston, and a second damping member installed in the damping housing to contact the second reaction piston. The second damping member is configured with an upper damper and a lower damper.