Electrocardiogram（ECG） signals are vulnerable to interfere with power frequency signals

which has always been a problem in signal acquisition. Aiming at the above problem

design a sam-pling system with high attenuation.The system uses XC3SD3400 A as core control-ler.The ECG signals are filtered through the notch and filtering modules

and are sampled and filtered with the 16-bit AD7656.The sampling data are cached

transmitted through the USB

and processed in the upper computer. Qualitative and quantitative analysis prove that with the designed system

the frequency signals are attenuated by 300 times

and the output signal to noise ratio（SNR） is greatly improved.To sum up

this system has the advantages of high noise attenuation

low useful information loss and high-precision sampling.