Electrocardiogram (ECG) has been widely used in studying the characteristics of human cardiac electronic activities and the diagnosis of cardiac related diseases. Conductive paste or gel was usually used in conventional wet contact electrode. However, it may cause burden, discomfort and skin allergies to the subject, which make it not suitable for long-term monitoring of ECG signals. To address this issue, this paper proposed a non-contact electrode which obtains the ECG signal through the capacitive coupling between skin and electrode sensing layer. Additionally, a physiological signal acquisition system based on ADS1299 was also built, so that a paste-free, non-contact ECG measurement could be achieved. Then, the effects of material and thickness of the insulating layer between non-contact electrode and skin on the ECG signal measurement were systemically investigated. The results show that the non-contact electrode can obtain high-quality ECG signals, and the insulation parameters have significant effect on ECG signal quality. Specifically, ECG signal quality achieves the best when cotton material was used as insulation layer. It was also observed that the smaller insulation thickness, the better ECG signal quality. The results of this study could provide important experimental and theoretical basis for further application of non-contact electrodes in mobile healthcare monitoring.