Intralingual contrast and comparison is an effective teaching method, which introduces the learning from what students have mastered to what they are going to learn. This study applied intralingual contrast and comparison on the teaching of English relative clauses introduced by relative pronouns for Chinese Senior high school students. Quasi experimental research design was used with 90 students, where experimental group received the new teaching method of intralingual contrast and comparison while control group received traditional teaching method (presentation, practice and produce). For better investigating the effect of new teaching method and exploring students’ challenges involved in learning ERCs, both quantitative and qualitative research methods were utilized in this study. The Data was collected via the experimental research (n=90) and semi-structured interviews (n=6). The findings revealed that the students of experimental group performed significantly better than the control group in the posttest, highlighting the effectiveness of the intralingual contrast and comparison teaching method on English relative clauses. Besides, the findings also revealed students’ challenges in learning English relative clauses, namely difficulties in rules memorization, short vocabularies and to judge what relativize to utilize. The study has provided implications for instructors for teaching English relative clauses.