This paper proposed a load balancing method for a multi-terminal back-to-back flexible interconnection system.Firstly,the flow control model of multi-terminal back-to-back flexible interconnection system is established,and the dynamic load rate,load following degree,feeder load evaluation coefficient and other indexes are defined.The load balancing system from single feeder to multiple feeder is established.Secondly,the improved cuckoo search with large searching range and high precision is optimized for the balanced system solution of multi-terminal back-to-back flexible interconnection system.Finally,an example is given on MATLAB to verify the necessity of dynamic load rate of multi-terminal back-to-back flexible interconnection system,the feasibility and effectiveness of load balancing.