The invention provides a Y/y0 three-phase voltage transformer error detection method for neutral point ground potential approximation. When a three-phase voltage transformer in Y/y0 wiring mode is detected, a program-controlled digital three-phase voltage power source, of which the amplitude symmetry degree is smaller than 0.2% and phase symmetry degree is smaller than 0.2 degree, is adopted, and thus the problem of symmetry degree of a three-phase voltage power source is solved; through three fully-insulated three-phase boosters, the accuracy degree of which is 0.02%, the problem of symmetry degree of the three-phase booster output voltage is solved; three electrical conductors, the accuracy degree of which is 0.2%, are adopted as secondary loads of the three-phase voltage transformer, and thus the problem of symmetry degree of the secondary loads of a test object three-phase voltage transformer is solved; and since the electrical conductors are adopted as the secondary loads of the three-phase voltage transformer, the problems above are solved effectively. Through detection equipment of existing three standard voltage transformers, the accuracy class of which meets detection requirements, and a transformer error detection device and the like, neutral point ground potential approximation of the test object three-phase voltage transformer can be realized. The method has the advantages of being scientific, practical, high in operability and low in cost and the like.