The invention relates to an error influence test method for extra-high-voltage CVT (capacitor voltage transformer). The test method can be utilized to measure voltage measurement error of the extra-high-voltage CVT under the influence of a proximity grounding body. The apparatus includes a voltage regulator, a transformer test, a standard transformer and an equipotential shielding capacitor voltage transformer test piece (CVT) and a grounding body; the primary side of the test transformer is connected with the voltage regulator; one end of the secondary side of the test transformer is grounded, and the other end of the secondary side of the test transformer is connected with one end of a current limiting resistor R; the other end of the current limiting resistor R is connected with the primary side of the standard voltage transformer and the primary side of the CVT; and the secondary side of the standard voltage transformer and the secondary side of the CVT are both connected with a transformer calibrator. With the test apparatus and test method of the invention adopted, whether the accuracy of the CVT can still satisfy a requirement of high precision when proximity equipment is grounded under a situation that a proximity grounding body exists can be verified successfully through simulation, and whether error generated by the above circumstance is smaller than that of a traditional structure CVT can be verified successfully through simulation.