There are always interferences in environment, especially power-line interferences, when we collect biomedical signals such as electrocardiogram, electromyogram and electroencephalogram. Moreover, the noise amplitude is usually much larger than that of the physiological signals, making the subsequent signal analysis and processing very difficult. The conventional methods are to pass the collected signal through a software filter for reducing the effects of power-frequency interferences. However, it would cause the reduction and distortion of the target signal. In order to solve this problem, this study proposed a novel design of hardware circuit based on the shielding technology, which can intensively inhibit the power-frequency interferences mixed in the original signal in analog front end. The experiments of both electrocardiogram and electromyogram acquisitions carried out on TI ADS1299 platform showed that the power-line interferences could be significantly suppressed when the electrode was electronically shielded. By comparing the conditions when the shielding layer was connected to different driving signals, it was found that the attenuation of the power-frequency interferences could reach as high as 35 dB when the electrode was shielded by signal itself. The shielding technology proposed in this study could be used in a variety of biomedical signal acquisitions to reduce power-frequency interferences at the initial stage, and therefore it could essentially enhance the signal to noise ratio of biomedical signals.