A non-contact electrocardiograph (ECG) measurement system based on capacitive coupled electrodes is proposed. Unlike conventional wet electrode, the capacitive coupled electrode is designed to measure ECG signal both in contact with skin and through clothes. The hardware part of the system includes two capacitive coupled electrodes, a reference electrode, a signal processing module and a transmission module, and the software part includes data extraction, signal processing, data storage, and waveform display. A real-time ECG denoising algorithm is developed based on wavelet transform with a moving window. To verify the performance of proposed system, two different conditions of the ECG measurement are experimentally tested in comparison with Ag/AgCl electrode. One is in a contact condition in which capacitive coupled electrodes touched the skin. Another is the non-contact condition in which ECG was measured through thin clothes. The results show that the capacitive coupled electrode is better than the conventional Ag/AgCl electrode when it is attached to the skin, and the clear ECG waveform can be obtained under non-contact measurement. The results demonstrated the feasibility to measure high resolution ECG waveform with real-time denoising algorithm in a non-contact way.