One of the major challenges of control flow analysis in decompilation is to structure 2-way branches into conditionals, loop conditionals and switches. In this paper, we propose a graph-based method to formally describe structures of 2-way branches via the introduction of concepts called "compound branch subgraph" and "cascade branch subgraph". We then present novel structuring algorithms based on such concepts. Compared with previous works, our algorithms are deterministic rather than heuristic, and they do not use complicated data structures such as Interval/DSG. We show that in theory our algorithm is more accurate and efficient than typical current approaches; furthermore, we have applied the algorithm to several real-world binary executables, and experimental results validate such theoretical analysis.