The readability level of a text is very important for students' comfort and development in learning English. This research aims to analyze: (1) the readability level of reading texts in the English textbook entitled "Smart Path to Learning English" based on Coh-Metrix for grade XI Vocational High School and (2) the factors that affect the readability level of texts in the textbook entitled "Smart Path to Learning English" for grade XI Vocational High School. This research used descriptive qualitative. Analyzing the content of several reading texts in an English Textbook. The main data of this research is from 20 reading texts in an English textbook entitled Smart Path to Learning English. The data was collected and further examined through analysis using software and manually to measure readability called Coh-Metrix. The results indicate: (1) out of 20 texts, there are only four texts (25%) that match the level of the students in this study which is grade 11. Sixteen (75%) texts are below the target grade level of the students. (2) there are similarities in theory regarding the factors that influence the readability level of reading texts in the English textbook "SPLASH" for grade 11 Vocational High School, namely: Lexical knowledge, organization of the text, discourse phenomena, and structural elements. The Researcher suggests that if there is a lack of reading material appropriate to the student's grade level, the teacher can choose another text that has a readability value close to the readability level of grade 11 students by considering factors that can influence the readability level of a text.