中文摘要：

六角系统是没有割点的连通的有限平面二部图，其每个内部面都是由边长为单位长的正六角形所围成，关于六角系统的各种代数与组合的性质已被数学家和化学家广泛地研究，本文证明了两类六角系统是2-共振的充分必要条件，并给出了两类2-共振六角系统的实例。

英文摘要：

A hexagonal system, also called benzenoid system, or benzenoid, is a finite connected plane graph with no cut-vertices in which every interior region is bounded by a regular hexagon of side length 1. Various algebraic and combinatorial properties of hexagonal systems have been extensively treated by mathematicians and chemists. In this paper, we give the necessary and sufficient condition for two kinds of hexagonal systems being 2-resonant, and construct two kinds of 2-resonant hexagonal systems.