In the field of second language acquisition (SLA), motivation of second language learners is of great importance to the research of the language, the learners and the learning situation. When "Chinese heritage students" (hereafter CHL students), and students learning Chinese as a foreign language (hereafter CFL students) study Chinese in the same classroom, their motivation of learning Chinese has drawn researchers’ attention. Drawing on theories on motivation of second language acquisition, this study explores how different factors influence Chinese language learners' motivation by qualitative case study. The results indicate that students' Chinese language and culture exposure explains their choice of learning Chinese in college and determines their basic learning goals (goal); that students' perceptions of their own language proficiency reflect the directions in which they would put more effort and their need for achievement (effort and want); and that the situational factors of the learning environment, such as the course, the teacher, and the groups, all influence students' learning motivation (attitude towards the activity). Based on the result that teachers can influence students' learning motivation through activities in the classroom, this study gives teachers and researchers some pedagogical implications about how to strengthen Chinese language learners' motivation in the learning environment.