Abstract: Many events happen in cities are distributed along the road network. Thus traditional space-time interaction tests often produce biased results. In this paper a network-constrained spatial weight matrix is formalized，and weighted according to the inherent properties of city events. This matrix is applied to the Baker's modified Knox test. The results show that with this new matrix, test methods are more flexible and net work-based when measuring space-time interaction intensity. For city management decision makers，this is a new approach for space-time interaction tests under road network constraints.