An analysis is made on the structure of ＂huo ＋ Adj/V ＋ si＂ in Hebei Mengcun Dialect. The meaning of the structure is ＂to achieve the ultimate degree＂. The words that constitute the structure are mainly adjectives indicating nature, verbs indicating psychological activities and some verb-object structures. From a historical view, the structure ex- perienced a process from ＂shengsheng/huohuo ＋ v＂, to ＂shengsheng/huohuo ＋ v ＋ si＂, then to ＂shengsheng/huohuo ＋ adj/v ＋ si＂, among which ＂huo＂ and ＂si＂ have gradually blurred into adverbs of degree. The structure of ＂huo ＋ adj/v ＋ si＂ are currently existing in a few dialects.