Critical thinking (CT) has been listed as one of the core competencies for English majors. One way to develop English majors CT is to infuse CT instruction into the intensive reading course. This paper reports on a three year collaborative action research study that systematically cultivated students CT skills and language skills simultaneously in an English intensive reading course. The study focused on three rounds: infusing CT instruction into intensive reading instruction, enhancing the explicitness of CT instruction, and adopting conceptbased instruction with appropriate instructional scaffolding. The results indicate that these three rounds of action research were significantly effective, not only improving students language abilities but also enhancing their CT skills.