A portable electronic device includes a main body and a card connector assembly mounted inside of the main body. The card connector assembly includes a base including a protrusion and a protrusion plate, a cover, and a movable plate. The protrusion includes a plurality of contacts. The protrusion plate includes an electromagnet. The cover is rotatably connected to the base, and includes a retaining member for retaining an electronic card. The movable plate is slidably connected to the protrusion plate, and is made of magnetic material. When in use, the cover is rotated until the electronic card contacts the contacts, the electronic device controls to power for the electromagnet, the electromagnet generates a magnetic field which drives the movable plate to slide toward the protrusion along the protrusion plate until the movable plate moves below the cover to prevent the cover from rotating in one direction.