In the present study, we performed synthesis of peptide polymer such as collagen and elastin model peptides. We examined rapid microreaction by using chaotic micromixer. By this reactor, we could obtain very high molecular weight species (Mn = 200000 for collagen and 160000 for elastin) with very narrow molecular weight distribution (Mw/Mn = 1.05) by reaction at relatively high flow rates. These result indicates that microreactor with chaotic micromixer is suitable for precise synthesis of peptide polymers. © 2008 CBMS.