In this paper, we implemented a low-power low-noise ECG acquisition system for heart disease identifications. The ECG signal is acquired with an analog front-end circuit, and the offset and baseline drift is eliminated at the same time. We also implemented a digital signal processing (DSP) unit to effectively remove EMG interferences. Interception of ST segment is proposed to achieve the identification of heart diseases. The ECG front-end chip has been designed and fabricated by using a TSMC 90nm CMOS technology, the total power consumption was measured at 40.3μW. DSP algorithms are carried out in the FPGA. Experimental results show that the sensitivity and specificity of ST segment classification after EMG elimination is 96.6% and 93.1%, respectively.