The graft copolymer with semi-interpenetrating polymer networks (semi-IPNs) from 2-hydroxyethyl methacrylate (HEMA) and natural rubber (NR) latex was prepared using cumene hydroperoxide and tetraethylene pentamine redox initiator system. The changes of grafting ratios and grafting efficiency with the reaction time and temperature, the concentration of crosslinking agent, initiator and monomer were investigated. The appropriate amounts of crosslinking agent (0.1phr), initiator (0.2phr) and monomer (20phr) and the optimum reaction conditions of 16ºC×8h were determined. The swelling temperature and times of monomers against NR latex particles were found to be significant for the grafting copolymerization and the appropriate swelling conditions were 16ºC×20h. The water contact angle measurement and platelet adhesion evaluation indicated that the hydrophilicity and blood compatibility of NR latex could be improved by grafting copolymerization with HEMA.