In order to explore the destructive impact on insulation，the inputting transient electromagnetic forceof a dry-type air-core shunt reactor model BKDK-20000/35 is numerically solved with the ANSYS electromagneticcircuit coupling finite element analysis method. The possibility of insulation failure caused by transient electromag-netic force is also discussed. Research results show that the transient over current generated by inputting the reactorcan produce a strong transient electromagnetic force，which is distributed extremely uneven. The axial electromagnetic force is symmetric about the center height. The farther the height is away from the center height，the biggerthe axial electromagnetic force is. The radial electromagnetic force points to the center coil which is on the center ofmagnetic field lines. The farther the coil is away from the center coil

the stronger the radial electromagnetic forceis. The axial electromagnetic force has a small effect on the insulation，while the radial electromagnetic force hassome damages to insulation. The delaminating between coils and envelopment insulation may lead to insulationcracking