The invention discloses a time delay detection system for a signal circuit. According to the time delay detection system, a first microprogrammed control unit controls a signal generator to generate two paths of signals; one path of signal is inputted to a second comparator directly, and the other path of signal passes through a measured signal circuit and is inputted to a first comparator; the two paths of signals which are outputted by the two comparators are inputted to a complex programmable logic device (CPLD); the output of the CPLD is connected to a second microprogrammed control unit; and the second microprogrammed control unit (MCU) 2 is connected with a thin film transistor (TFT) touch screen and a secure digital (SD) card for storing information. In a CPLD time delay detection unit, a dual-input time difference measuring method is adopted in the measured signal circuit, so that the measurement of a broadband signal can be ensured; the frequencies and amplitudes of the signals generated by the signal generator can be adjusted; and the signals with different frequencies can meet different measuring requirements, and the signal time delay characteristics of different signal unit circuits can be measured. According to the time delay detection system, time delay characteristic curves of different signal circuits within a certain frequency range can be measured, and can be stored to the SD card to be inquired historically and conveniently.