DC bias of transformers in power grid due to GIC broadly happens in the whole world. Under the effects of GIC

the simultaneous increase in the reactive power loss of transformers in the whole grid may cause grid voltage instability. Studying the methods for calculating the GIC-related reactive power loss（GIC-Q） of kinds of transformers is one of basic means of knowing and preventing harmfulness to power grid due to geomagnetic storm. To prevent the geomagnetic storm hazard in UHV power grids

we review methods of calculation and their research progress of GIC-Q of high voltage and extra-high voltage transformers including engineering and theoretical algorithms

both at home and abroad. Besides

the requirements of engineering and theoretical algorithms of single-phase four-limb and single-phase five-limb UHV transformers’ GIC-Q are analyzed. Finally

the problems of methods of calculation for the GIC-Q of UHV transformers and large-scale power grid are put forward

which need to be solved urgently.