The As-level topology is a hotspot of the recent reseaches. We can understand the centralization of the network clearly by researching the evolvement trend of the Internet macroscopic topology. The massive data we use in this paper is from CAIDA (The Cooperative Association for Internet Data Analysis) Skitter project. And the time span of the data is from July, 2001 to January, 2008. This paper introduces the background of the AS-level topology at first, then carries out the evolvement of degree, core and layer. It is believed that the influence of the top-degree nodes on the other nodes decreases and the centralization of network is going to fall off with the decrease of the core. And the nucleus status of network declines.