Researchers point out that the students at Technological Universities have insufficient vocabulary sizes. In addition, the vocabulary sizes of freshmen at the surveyed technological university in the south of Taiwan are ranged from 769 to 1450 words recognized as the level of 8(superscript th) graders. Textbooks written in English and frequently used in the universities might not be appropriate for students at technological universities. The researcher found his students from the Department of Electronic Engineering could not read English textbooks independently with lower vocabulary sizes around 1000 words, less than 1500 words,. The purpose of this study aimed at investigating the sizes of students' vocabulary by understanding the reasons for their deficiency, and discovering possible solutions to help students heighten their learning motivation and build confidence in learning larger vocabulary to meet the needs of reading English textbooks in their chosen fields.