There is little research on the task-based teaching approach in senior secondary L2 English writing classrooms. This study carried out an exploratory sequential mixed methods study to explore the suitability and adaptations of task-based language teaching in the domain of secondary schools in small cities. First, the researcher surveyed six EFL senior secondary teachers of different teaching experiences in China by convenient and purposive sampling to get background information, then had semi-structured interviews with them individually. To followed the interviews, the researcher surveyed 148 students via an online questionnaire also by convenient and purposive sampling. Findings indicated that, although most teachers acknowledged the usefulness of TBLT, they regarded it unsuitable and unfeasible in the context of Chinese senior secondary L2 writing classrooms. Also, students in the study ranked clear instruction and vocabulary increase as the first two contributors in improving their L2 English writing. But half of all students also valued an interesting writing classroom and took it as a third facilitator to develop their writing. Besides, adaptations were suggested to include professional task design, teacher discussion, reward mechanism and teacher profession development. In the future, further research is needed to examine the findings in this study, generalizing them to different contexts, ages and domains, and exploring teachers’ individual differences and their choice of teaching approaches.