A judgment method of line breakage of a special TV for inter-turn protection of a generator comprises the following steps: a generator terminal is provided with a general voltage transformer TV1 and aspecial voltage transformer TV2 for inter-turn protection; a protection device is used for sampling secondary side voltages of the voltage transformers, thus respectively obtaining negative sequencevoltage 3U2 of the TV1, negative sequence voltage 3U2' and foundational wave zero sequence voltage 3U0' of the TV2 based on holocycle Fourier filtering and calculation; and fixed values U2.set1, U2.set2 and U0.set2 are preset inside the protection device, wherein, 3U2 is smaller than U2.set1(1), 3U2' is greater than U2.set2 (2) and 3U0' is greater than U0.set2 (3). When meeting inequations (1)-(3)simultaneously, a line breakage alarm signal of the TV2 is generated after short delay t1, and the inter-turn protection is locked; and if the TV2 has no line breakage later, that is, that is, the inequations (1)-(3) can not be met simultaneously, line breakage alarm of the TV2 is canceled after long delay t2, and longitudinal fundamental wave zero voltage inter-turn protection is re-started.