A sensor used by a smart magic cube is disclosed. The sensor includes: a stator configured to be fixedly disposed on the smart magic cube; a first rotor rotatable in synchronization with a first magic cube layer of the smart magic cube, such that when the first rotor rotates with the first magic cube layer with respect to the stator, the stator or the first rotor outputs a rotation signal of the first magic cube layer; and a second rotor rotatable in synchronization with a second magic cube layer of the smart magic cube, such that when the second rotor rotates with the second magic cube layer with respect to the stator, the stator or the second rotor outputs a rotation signal of the second magic cube layer. A smart center shaft, a smart magic cube and a monitoring method for the smart magic cube are also disclosed.