Blended learning utilizes the affordances of information and communication technology to integrate online learning with face-to-face teaching. It facilitates to meet students' disciplinary learning needs and helps them achieve the intended learning outcomes so that they can advance in their professional study. The present study focuses on developing and evaluating a blended course implemented in the context of English for Specific Purposes (ESP) from the perspective of accountability and development, with the purpose of assessing the effectiveness of the course from three aspects: the satisfaction of students' learning requirements, the achievement of their learning outcomes, and the ongoing refinement of the course. Data of the course evaluation survey were quantitatively analyzed by descriptive statistics and data of students' learning reflections were qualitatively analyzed by thematic analysis. Results indicate that, firstly, students are satisfied with the course design and its implementation; secondly, the course modification should focus on adding academic presentations, teaching in English with trans-semiotising approach and consolidating the disciplinary community, which in turn activate students' knowledge-sharing and critical thinking. The study offers a systematic framework to evaluate the ESP blended course, which also has implications for evaluating blended courses in other language curricula.