New complete BVR light curves of the contact binary AR Bootis (AR Boo) are presented. They are analyzed through the 2013 version of the Wilson-Devinney (W-D) code. Our new photometric solution shows that AR Boo is a W-subtype W UMa contact binary system with a mass ratio of q = m(2)/m(1) = 1.865 and a fill-out factor of 12.7%. The changes in the orbital period of AR Boo are analyzed. It is found that the orbital period of this binary has a continuous increase at a rate of 2.04x 10(-7) days yr(-1), together with a cyclic variation (with a period of 39.05 yr and an amplitude of 0.0154 days). We discussed the mechanism responsible for the changes in the orbital period of AR Boo. It is found that the long-term increase in its orbital period is caused by mass transfer from the less massive component to the more massive one, and the periodic variation in its orbital period might be a result of the light-travel-time effect owing to a third body or the magnetic activity in the more massive component of AR Boo.