There exist negative effects between the control commands and control targets of the automatic generation control（AGC）and automatic voltage control（AVC）system，which is apt to result in such problems as system security and overshoot.By adopting the decomposition-coordination method between active frequency and reactive voltage based on time dimension，a coordinated automatic control system of AGC and AVC based on hierarchical control is built.The design scheme of each control layer is also given.The upper controller optimizes and coordinates active and reactive power，and provides economical，safe，and optimal reference setting trajectory.The lower controller improves the control strategy of AGC in advance thus realizing comprehensive energy saving.And a study of the AGC effects to be exerted on voltage control is made.By means of the corresponding reactive voltage control command，optimal coordinated control of the economy and security of the power system are realized，enabling the system to operate in the multi-objective sub-optimal region.Meanwhile，the AGC and AVC commands should be checked and revised by employing the staggered iteration concept to obtain the comprehensive coordination command and minimize the negative effects of the two on each other.The effectiveness of the control system，strategy and method proposed is proved by computer simulation results.