A deviation compensation method of a potential transformer is provided. The deviation compensation method includes: providing first to Nth potential transformers to be installed at different locations in a high voltage direct current (HVDC) transmission system; supplying a first voltage to the first to Nth potential transformers provided; measuring voltage values output through the first to Nth transformers by the first voltage supplied; determining whether there is a deviation between the measured voltage values; and determining compensation values for correcting the measured voltage values to the same voltage value when there is the deviation.