Heart diseases have become more and more prominent in recent years. ECG signals can accurately reflect the health of hearts during the detection process. The use of wearable ECG devices requires low power consumption, a high common-mode rejection ratio, and minimal noise. Traditional research has concentrated on lowering the circuit's overall power dissipation, which typically results in less current flowing through the amplifier but higher circuit noise. Therefore, this places higher demands on the amplifier in the circuit. Electronic devices are becoming smaller due to the rapid development of semiconductor technology. Amplifiers designed for semiconductor devices can effectively solve the problems mentioned above. The circuit created in this study has a low power need, a high common-mode rejection ratio, is compact, has a high input impedance, and has a low input-referred noise level. In addition, LT-Spice software was used to design and simulate the circuit, and the results were analyzed and calculated accordingly. The circuit meets the requirements of the project design. The frequency range of the circuit is 1mHz - 227.9Hz. The differential gain of the circuit is 36.6dB. The integrated input-fred noise is 3.94uV. The total consumption of electricity is 4.67W. These data indicate that the circuit has a high gain in the frequency range of ECG signals, which can filter out other interference signals. It also solves the problems of power consumption and noise.