A power ramp for a vehicle and a control method thereof are disclosed. A power ramp for a vehicle includes a main frame defining an exterior appearance thereof, a base plate provided in a bottom of the main frame to define a base of the main frame, a main ramp provided on the base plate, a ramp holder having an end hingedly coupled to the main ramp to support the main ramp, at least one sliding part provided in right and left end portions of the main frame to guide forward-and-rearward motion of the ramp holder, a pair of power generating device provided in the ramp holder to supply power required for the forward-and-rearward motion of the main ramp, a pair of sliding chains longitudinally provided along the right and left end portions of the main ramp, the pair of the sliding chains supporting the main ramp to be movable forward and rearward, and a manual operation changing part provided in the main frame, the manual operation changing part selectively controlling rotation of the sliding chains to enable the main ramp to be movable manually.