The invention discloses a turbine generator winding turn-to-turn short circuit diagnosing method based on a cross-core bolt. The method includes: taking one section of the cross-core bolt of the stator iron core of a generator, outwardly guiding measuring lines out of two ends of the section of the cross-core bolt through the inter-section gaps of the stator iron core, and collecting the induction voltage of the cross-core bolt through the measuring lines; using an online collecting system to collect the induction voltage of the cross-core bolt in real time, and performing real-time data processing on the collected induction voltage to obtain the percentage content of corresponding harmonic waves relative to fundamental waves, comparing the percentage content with a set threshold, and judging that the turbine generator has the rotor winding turn-to-turn short circuit fault when the relative content of the corresponding harmonic waves exceeds the set threshold. By the turbine generator winding turn-to-turn short circuit diagnosing method, the technical defects in the prior art are overcome, and the diagnosing level of the rotor winding turn-to-turn short circuit fault is raised.