We have developed a real-time arrhythmia detection system using four vaviables;heart rate, QS width, morphology and axis. Because of difficulties in real-time operation on the frequency domain, time domain process are carried out. The sampling rate of the ECG signal is 240/sec by using 12 bit A/D converter and we design digital comb filter to avoid 60Hz AC interference and DC drift. The band width of the digital comb filter is 1.79 Hz and Q is 64. To design a QRS detection logic, an 8 to 20 Hz bandpass filter is design on the basis of the power spectrum of the QRS complexes derived from the simulators and patients'data. By feeding the filter output into an adaptive threshold comparator, no detection of false QRS or T waves are found, and an accurate heart rate detection is obtained.