Flexible Loop Network Controller (FLNC) is applied to interconnect multiple AC distribution networks into a loop network, which can realize active and reactive power independent decoupling control, improve system security, decrease operating risks, etc. On this basis, a power model and boundary conditions of three-terminal FLNC for power dispatch of distribution network is presented. First, through building the model of three-terminal FLNC for power dispatch, the power relationship formula is presented. Second, the boundary conditions of power dispatch are theoretically analyzed. Then, the scope of power dispatch needed in engineering practice is obtained through an idealized model, and the power dispatch modes considering comprehensive security boundary conditions are established. According to two different situations, the power allocation results which can meet the different conditions are proposed. Finally, the simulation results verify the effectiveness of the three-terminal FLNC power dispatch model and the boundary conditions. This work is supported by National High-tech R & D Program of China (863 Program) (No. 2015AA050102).