The effect of English Medium Instruction (EMI) on language learning has been a classic and extensively discussed topic in EMI research, with various methods used to address it. One reliable method is corpus-based analysis, which provides quantitative evidence about the development of learners’ linguistic competence within an EMI context. This paper chapter aims to introduce the application of corpus-based analysis in EMI research through three tasks. Firstly, it summarizes relevant literature exploring the effects of EMI on English learning. Secondly, it elaborates on how to use corpus-based analysis to conduct relevant studies, including corpus construction, linguistic analysis instruments, and statistical analyses. Lastly, it presents an example study that demonstrates the value of corpus-based analysis in EMI research. The study examines learners’ longitudinal development of phraseological competences within an EMI course and explores the effect of textbook input on language learning. The data for the study consisted of learners’ written productions at three data collection times in the course. Learners’ phraseological competence was measured by eight measures targeting bi-grams’ and tri-grams’ complexity. The study found noticeable growth in learners’ phraseological competence with EMI education’s progression and similarities between high-frequency bi-grams and tri-grams in textbook input and learners’ written productions, proving the effect of the input on language learning.