Abstract：When studying the growth mechanism of industry clusters, most researchers put their emphasis on the inner factors. Here, the angle of vision for the reseach is expended to the spatial relationship among industry clusters and an analytic framework for the study of cluster growth is established based on the factor endowment and spatial relationship. The data of three years from 54 state-level Science and Technology Development Zones (STDZs) in China were analyzed and some instructive conclusions were drawn as follows: In addition to the human resource capital, endowment of cluster factors plays a crucial role for promoting cluster growth. Spatial relationship makes an essential contribution to the cluster growth. Cluster density, geographic proximity, and industry overlap among clusters can cause an inverted U-shaped growth pattern. Following these conclusions, some policy suggestions were put forward regarding STDZ establishment, location selection, industry positioning, and internal construction and management.