Many challenges arise in subgraph query processing of graph-structured XML data. This paper studies the subgraph query processing of graph-structured XML data and proposes. A hash-based structural join algorithm, HGJoin to handle reachability queries on graph-structured XML data. Then, the algorithm is extended to process subgraph queries in form of bipartite graphs. Finally, based on these algorithms and cost model presented in this paper, a method to process subgraph queries in form of general DAGs is proposed. It is notable that all the algorithms above can be slightly modified to process subgraph queries in form of general graphs. Analysis and experiments show that all the algorithms have high performance.