The disclosure discloses a main board, wherein the main board includes: a first pad; a second pad connected to the first pad; and a third pad connected to both the first pad and the second pad. The disclosure also discloses a method of implementing network/card locking, wherein the method includes: transmitting, by an encryption chip, a blocking request to a central processing unit when the encryption chip detects authentication-related information that is provided by a user identification unit to the central processing unit, and determines that the authentication-related information does not meet a preset network/card locking requirement from a mobile operator; blocking, by the central processing unit, the mobile terminal from normal operation when receiving the blocking request. Meanwhile, the disclosure also discloses a mobile terminal in which network/card locking is implemented, wherein the mobile terminal includes a central processing unit, a user identification unit and an encryption chip. By using the main board, the method and the mobile terminal of the disclosure, the costs for producing a mobile terminal which is respectively adapted to different sales modes of mobile terminals can be reduced.