In this paper, the method of comprehensive fault diagnosis based on fuzzy qualitative trend analysis is presented to address the problem of incompatibility of detection methods for JTC compensation capacitor and tuning area, realizing comprehensive fault diagnosis of JTC including compensation capacitor and tuning equipment. A simulation model of JTC compensation capacitor and tuning equipment faults was established based on the transmission line theory. The signal curve trends of JTC fault-free, and the compensation capacitor and tuning equipment at fault were extracted respectively according to the divided point of compensation capacitor position, with which a knowledge base was built. the matching degree between an actual signal and the classical failure mode in knowledge base according to the matching degree formula defined in this paper. Finally, the diagnosis result was given. Experiments shows that the higher the SNR(Signal Noise Ratio) is, the higher the diagnostic accuracy is. The diagnostic accuracy is as high as 94.9% when the SNR is 50 dB and corresponding ballast resistance is 1 Ω·km. The proposed method has a higher flexibility and applicability compared with the simulated annealing algorithm.