An ACC system and method for controlling a vehicle are disclosed. An adaptive cruise control (ACC) system includes: a radar sensor unit which detects an object around a vehicle and a movement detector which measures a driving speed and acceleration of the vehicle and a determination unit which determines a stopped object to be a stopped vehicle when the stopped object is detected in front of the vehicle and a surrounding vehicle detected around the vehicle is detected to decelerate on the basis of the measured driving speed and acceleration and a controller which regards the stopped vehicle as a preceding vehicle and performs deceleration control.