Abstract: As an important index of power system operation, the fluctuation of reactive power affects the safe and stable operation of power equipment as well as the voltage stability of the whole system. In order to analyze the reactive power distribution of three-phase five limbs transformer under the action of geomagnetically induced current, we established the magnetic field circuit coupling finite element calculation model of three-phase five limbs transformer according to the actual parameters of the transformer and by means of the series resistance and voltage compensation, and thus quantitatively analyzed the reactive power of the transformer under different sizes of geomagnetically induced current. By calculating the distribution of reactive power under three-phase five limbs no-load and rated load and the reactive power of single-phase autotransformer, we find that with the increase of geomagnetically induced current, the reactive power characteristic curves of three-phase five limbs no-load and load increase linearly, and the reactive power curve of single-phase autotransformer is more sensitive to geomagnetically induced current than that of three-phase five limbs transformer. Moreover, we analyzed the reasons for the variation of reactive power difference by combining the magnetic circuit characteristics of transformers with different core-limb structures. The research results can provide reference for the stable operation of three-phase five limbs transformer under the action of GIC.