Legal English has been catching people’s attention. Plenty of textbooks emerge in recent years. This passage focuses on the vocabulary in the reading texts as well as the difficulty of texts. Taking the textbook Legal English (2011) as an example, the author builds the corpus of the reading passages in the Text Section and the Supplementary Reading Section. This research investigates vocabulary range of these reading passages as well as the interrelationship between these ranges. The research instrument is Range Program which measures vocabulary distribution and Coh-Metrix 3.0 which tests the difficulty level. The expected result is that vocabularies may be centered in the first three wordlists. Such kind of finding may draw the implications for textbook design. Compilers may need to enlarge the vocabulary differences of distribution and represent the difficult gradients to significantly enrich students’ vocabulary knowledge. And the difficulty level is supposed to be similar among the units.