“权力三项”是语义建构和知识积累的重要语言资源。本文以国内某套大学英语教材为例,对科普、社会、文学语篇的权力三项特征作了对比分析。其结果表明:科普语篇的权力三项特征最为明显,各种资源互相配合,形成典型的语义波信息周期性;社会语篇的语义密度稍低,信息周期性不如科普语篇典型;文学语篇由于其特定的叙事手段,权力三项特征不大明显。本研究结果有助于大学英语教师认清不同学科知识的语码特点,以提高教学质量。 “Power of three ” is an important linguistic resource for semantic construction and accumulation of knowledge. Taking a certain set of college English teaching materials as an example, this paper makes a contrastive analysis of the three characteristics of the power of popular science, society and literature. The results show that the three characteristics of the power of science discourse are the most obvious, and all kinds of resources cooperate with each other to form the typical cyclical of semantic wave information. The social discourse has a lower semantic density and cyclical nature of information than the typical science-based discourse. Because of its specific narrative means, the three characteristics of power are not obvious. The results of this study help college English teachers recognize the code features of different disciplines in order to improve their teaching quality.