Abstract: To detect the fast logic pulse sequence related to random events, an online detecting system has been realized based on a 1 GHz ultra-high-speed A/D converter and a high-speed FPAG processor.PeakTDC algorithm was designed to seek the peak position of the pulses and therefore demarcate the corresponding pulse time, and then to form the time code and peak amplitude for the pulse sequence. The practical test results of the system show a time interval error of 1 ns, a peak amplitude error of 2 quantization units, and a paired pulse resolution of 10 ns. The algorithm theory and experimental results demonstrate that the system can achieve ns-level time-digital-conversion for random pulse sequences on a limited long time-bin, and simultaneously obtain the peak value of pulses.