Abstract: A dynamic generation method is presented based on arc graph grammars of Rivas and Eddy（R&E） RNA secondary class to calculate the genus of RNA secondary structure graph. Comparing with the determinant method for calculating genus, the presented method mainly has two advantages：the first one is the improvement of the efficiency of genus calculation, the second one is the generation of the mini-genus graphs of RNA secondary structures.

Key words: pseudoknots, RNA secondary structures, topological classification, genus

摘要： 基于Rivas和Eddy（R&E）RNA二级结构类的图语法，提出了一种计算RNA二级结构图亏格的动态生成算法。与已有的基于判定的亏格计算方法相比，该算法的优点主要有两点：一是提高了计算亏格的效率，二是可以实现枚举小亏格RNA二级结构图。

关键词: 假结, RNA二级结构, 拓扑分类, 亏格