Hi jianguo_88,
Your question seems to be Arduino related and not Edison. I think the best option is to post your question in the Arduino forum: Arduino Forum - Index
Additionally, I will suggest you to check a tutorial that I saw last week in Sparkfun; it might be interesting for you since it seems to be very similar to your project: AD8232 Heart Rate Monitor Hookup Guide - learn.sparkfun.com. However, you should post your question in the Arduino forum.
Regards,
Diego.