Embodiments of the present invention disclose a method, user equipment, base station, and system for detecting sharing of a timing advance value, relate to the field of communications technologies, and solve a problem in the prior art that a normal service cannot be provided because a TA value cannot be shared between different uplink CCs. According to the embodiments of the present invention, the user equipment may determine, through a time offset between synchronization of downlink component carriers corresponding to uplink component carriers, that a too large time offset indicates that a same TA value cannot be shared; the base station may calculate a TA value directly through a dedicated preamble sequence, and then compares the TA value with a TA value of one of the component carriers, where a too large difference between the TA values indicates that a same TA value cannot be shared.