This study is aimed to get empirical and measures the readability of the reading texts in the English textbook Look Ahead 2 published by Erlangga for Senior High School Grade Eleventh students. The writer employed descriptive qualitative and descriptive quantitative method. The object of the study was the English textbook that contains six units, so there are six reading texts in the English textbook. To collect the data, the writer used cloze test as a measurement device. Based on the analysis of data result, the readability level of reading text for grade XI students of SMA published by Erlangga categorized instructional level. It means that the reading text is readable and suitable with students? ability in aclass. Finally, from this analysis that has been done in this writing, the writer concluded that the writers of English textbook and the publisher use the readability formula as the guidance to measure the readability level of reading texts. Then for the English teacher if there unreadable text they can change with the synonymous words as the students? level.