Abstract: Autonomous system (AS) relationships play a critical role in data transferring and routing in the Internet. From the perspective of AS relationships, a concept of AS diversity is first proposed and the development trend of AS diversity in recent years is studied. The result shows that Internet AS diversity has significant growth trends and their distribution become more and more extensive in recent years. Moreover, AS diversity is combined with the traditional parallel-series reliability model, and then a new path diversity model based on AS relationships, named SPDSA (series-parallel path diversity system based on AS relationship) model, is presented. The relevant SPDSA measure is given at a later time. Finally, many virtual multihoming sites which depend on route views node data are simulated and dynamic experiments of AS path diversity are performed by SPDSA measure. Test results show that SPDSA measure is superior to traditional measures and it is especially effective to identify AS path diversity based on multi-homed network. Furthermore, the experiment results also show that multihoming can enhance AS path diversity in the Internet. Finally, the results indicate that though AS diversity has significant growth trends, AS path diversity reveals no major changes in recent years.