The characteristics of the UHVDC/AC hybrid grid have put forward new demands on the construction of AVC system. This paper firstly analyzes four operating modes which AVC system needs to cope with when the disturbances occur in the AC gird and the UHVDC grid respectively with different time constants. According to that, the coordinated control strategy including adding the coordinated bus voltage constraints of the converter station, adaptively refreshing the voltage constraints in the AVC system, adjusting the optimal control calculation time as well as control objectives is given. On basis of the continuous AVC simulations on standard IEEE 39 example system and by comparing the system response before and after the coordinated strategy is adopted when the AC and UHVDC grids’ operation modes have changed, the coordinated control strategy will reduce the unreasonable switching times of var compensation equipment is verified. The proposed coordinated control strategy will be applied in Sichuan grid.