To improve the load following ability and enhance the coordination among NON-AGC units and base load off-regulated automatic generation control（BLO-AGC） units and base load regulated automatic generation control（BLR-AGC） units during peak load， the paper presents very short-term dispatch time scale and coordination strategy between online dispatch time scale and very short-term dispatch time scale. The BLO-AGC units regulation capacity is verified at the end of the very short-term dispatch time scale in a given current online dispatch time scale， and the BLR-AGC units regulation capacity is checked every very short-term dispatch time scale respectively. If BLO-AGC units regulation capacity is lack or BLR-AGC units regulation capacity is lack， then the coordination will be start up. Considering the problem of climbing peak load， frequency regulation and network security， the paper builds the coordination model between NON-AGC units and BLO-AGC units， and the coordination model is also built between BLO-AGC units and BLR-AGC units. Finally the feasibility of the new coordination model is proved by a practical system.