The study aimed to investigate the influences of differentiated instruction on English learning among junior high school students. The researcher analyzed target students’ traits and designed the learning environments, materials, strategies, and evaluation methods for differentiated instruction in the hope of helping students achieve their best English learning efficiency. The objects of study were eighth graders in Happy Junior High School. Based on the researcher’s futile efforts to improve students’ learning efficiency with the traditional teaching method in the seventh grade, the study attempted to apply action research to investigate differentiated instruction and focused on conversations in reading to design differentiated instruction, after the second midterm exam in the second semester of the eighth grade. The researcher integrated self-reflection, peer suggestions, dialogues with students, and feedback from students’ contact books, as the foundation for the following lesson plans. The findings were as follows. First, the success of planning and implementing differentiated instruction hinged on the researcher’s observation, dialogues with students, peer suggestions, and self-reflection in the process of research to make timely adjustments in the curriculum and teaching so as to design suitable learning environments, materials, and evaluation methods for students. Second, differentiated instruction combined with multilevel mind maps was beneficial in creating a positive English learning process and enhanced students’ performances in cognitive, affective, and psychomotor domains.