This paper presents the author's experience in the application of corpus concordance in helping the students in structure analysis class understand the construction of English sentences containing adjective or relative clause. The adjective clause is under discussion based on the pre-test scores on adverbial clause, non-finite clause, coordinative clause and adjective clause in which the students' score on adjective score was the lowest. In the realm of action research, a variety of data was collected, including the students' corpus search projects and reflection papers and teachers' teaching journals. A close analysis of the data reveals findings on the concordance lines showing how the keywords of the study namely relative pronouns are being used in the corpus. These concordance lines then are used by the students to explore the construction of English sentence containing the pronouns after some brief theoretical foundations about the concordance.