Being one of the most deployed payment channel networks (PCN), the lightning network (LN) has attracted much attention since it was proposed in 2016. The LN is a layer-2 technology addressing the scalability problem of bitcoin. In LN, participants only need to submit layer-1 transactions on the blockchain to open and close the payment channel, and they can issue multiple transactions off-chain. This working mechanism avoids the waste of time on waiting for every transaction to be verified and simultaneously saves transaction fees. However, as the time of LN put in practice is rather short, previous works were based on small volume and rapidly-changing data, which lacks necessary time-effectiveness. To fill in the gap and get a comprehensive understanding of the topology of LN and its evolving trend, this study characterizes both static and dynamic features of LN by leveraging graph analysis based on data of high time- effectiveness updated to July, 2020. A clustering analysis of the nodes is carried out, and some conclusions and insights derived of the clustering results are presented. Moreover, an additional study of the charging mechanism in LN is conducted by comparing the on-chain and off-chain transaction fees.