Current non-contact sleeping electrocardiogram (ECG) monitoring technology has a limitation when used to effectively acquire the multi-positional human ECG signals. This study developed a type of ECG monitoring system that can measure sleeping ECG signals under multi-positional conditions through clothes and bed sheets. A flexible conductive fabric is used as the electrode material. The shape of ECG electrode is similar as an arched door. The variation of electrical field is sensed by capacitive coupling. The ECG signals are coupled from human body to the fabric electrodes. Combined with a large resistance of 10 GΩ as a bias resistor, an instrumentation amplifier with high input impedance is used for differential signal processing. A digital filtering technology is used to remove the noise in the raw ECG signals, while the finite state machine (FSM) logic algorithm is applied to extract the features of ECG signals. The ECG signals detected from human subjects experimentally by the proposed system are compared with those detected by the strip-type noncontact ECG electrodes as well as traditional contact ECG acquisition system. Experiment results show that this system can obtain decent sleeping ECG signals under non-contact conditions, and the detection rate of R wave of ECG signal is over 95% .