The invention discloses a voltage transformer broadband error measuring method which comprises the following steps of parallelly connecting the primary side of a standard voltage transformer with theprimary side of a to-be-measured voltage transformer, and connecting the secondary side of the standard voltage transformer and the secondary side of the to-be-measured voltage transformer with an error measuring device; inputting a voltage signal to the primary side of the standard voltage transformer by means of a power supply device; calculating a second difference voltage and a voltage included angle by means of an error measuring device; calculating the ratio error and the angle error of the to-be-measured voltage transformer according to the secondary differential voltage signal and thevoltage included angle, and calculating the broadband error of the to-be-measured voltage transformer according to the ratio error and the angle error; determining whether the voltage value and the frequency of the primary side input voltage signal of the standard voltage transformer exceed a preset voltage value, and adjusting the voltage and the frequency according to a determining result. The voltage transformer broadband error measuring method improves voltage transformer error measuring efficiency and has relatively high measurement precision.