Abstract: During the medium maintenance of LM2500+gas generator or the field treatment of compressor impeller, the dynamic balance of the whole rotor is impacted, and consequently the reliability and stability of gas turbine-driven compressor unit and generator unit are influenced.In this paper, the structure and assembly process of LM2500+gas generator were investigated, and the cause of the unbalance was analyzed.It is indicated that during the medium maintenance of LM2500+gas generator, only the turbine rotor is balanced while the light point coordination of two rotors aren't taken into account during the assembly of the compressor rotor.As the unbalance and vibration of the whole rotor increases, the vibration of the compressor set is ultimately beyond the limit.Three-circle balancing method can be adopted to balance the rotor of LM2500+gas generator if the compressor of gas generator is not disassembled or professional equipments are lacking on site.Finally, a case study was carried out.It is revealed that three-circle balancing method is more complex in plotting the process of dynamic balance and lower in the accuracy of experimental data, but it can effectively solve the vibration of dynamic machinery, so it can be widely used for field operation.