Abstract: For the macro-topology which shows hierarchical characteristics in large-scale software, coreness distribution and the correlation with degree, the effect of nodes with highest coreness on each and every layer and the trend of software structure coreness evolution analyzed on the basis of a large number of statistics data on coreness of open source software architecture. The result reveals that the k-coremax of software structure is generally small, the coreness distribution is scale-free characteristic, and the nodes with highest coreness have powerful influence. There is a certain positive correlation between coreness and degree for low-degree nodes, however, the coreness does not increase with the growing degree when the coreness comes up to a certain value, and the k-coremax and software core architecture remain stable during software evolution.