Abstract: We explore the network structure of technology in biotechnology industrial clusters and how prior structure affects formation of ties among technologies from a network perspective. We select technology networks in Boston and San Diego from 1976 to 2006 as cases. Based on visualization techniques of networks, we find both clusters have a separate components structure pattern. We also observe a phenomenon of boom and decline of technology during the evolution process. Based on Negative Binomial Regression, we find that core position of global network has a positive relation with formation of ties. Effects of bridge position are different in two clusters. Evolution of clusters is an emerging process.