This paper presents an ultra-low power batteryless piezoelectric energy harvesting sensor node of acquisition electrocardiogram (ECG) data. This data acquisition system utilizes recent advances in piezoelectric energy harvesting, analog-to-digital convert –er (ADC), and data compression, and combines them to implement a batteryless and low power healthcare device. The measurement shows that ~20uW can be collected from the commercial piezoelectric plates with a 65kg person at a walking speed of 0.5 step/s. A 11-bit noise-shaping successive approximation register (SAR) ADC at a sampling rate of 25kHz with approximate 100nW power consumption can be achieved from simulation. In addition, a precision-configurable ECG compressor is proposed to reduce the dynamic power consumption. The corresponding compression ratio can achieve from 2.81 to 11.79, with percentage root mean square difference ranging from 0% to 0.62%, respectively. VLSI implementation consists of 3.25 K gates and the average power consumption is 863 nW with 180-nm CMOS process.