nodes and their interactions are abstract edges. This paper attempts to characterize the structural quality of complex software networks. We propose to use a novel statistical measure, called average propagation ratio, to characterize the structural quality of general complex software networks, such as software adaptivity and maintainability. Several real-world complex software networks are analyzed in some depth to demonstrate the application of average propagation ratios. Furthermore, we investigate the key factors that determine the average propagation ratios of general complex software networks, resulting in a set of guiding principles that can be used in practical network design for improving the structural quality of complex software systems.