Abstract: An access control system includes a portable user device, an access control apparatus and a portable administrator device. The access control apparatus includes a first near field communication (NFC) unit and stores a first valid user list. The portable administrator device includes a second NFC unit and stores a second valid user list. The first NFC unit and the second NFC unit are operable to enable communication between the access control apparatus and the portable administrator device, and the access control apparatus and the portable administrator device are operable to synchronize contents of the first valid user list stored in the access control apparatus and the second valid user list stored in the portable administrator device.