How can I find the number and names of professional cyclists who is
doubted to die from dosing in history? Especially in recently years,
after EPO appeared

This article, published in 1999, estimates the number of deaths at 80:

"When cycling doctors jumped into the fray and covertly started to
tinker with EPO dosing, the risk of cardiac arrest was greatly
reduced. Dr. Michele Ferrari, an Italian who was the chemical
architect behind some of cycling's most notorious teams, once told the
French sports daily L'Equipe that with proper supervision EPO is 'no
more dangerous than orange juice.' The long-term effects of EPO,
however, have yet to be determined, and Ferrari's statement is an
insult to the 80-odd riders who may have died as guinea pigs so that
the sport could learn how to cheat better."

http://www.salon.com/health/feature/1999/04/21/cycling/index1.html