Assessment as learning (AaL) aims to develop students' metacognitive awareness of their learning process, and promote their academic study and self-regulated abilities. The study investigates the benefits and challenges perceived by students regarding the implementation of AaL strategies in a general writing course in a Chinese university. The findings reveal that students benefited from the AaL-oriented instruction in terms of their improved writing efficiency and quality, enhanced assessment and feedback literacy, as well as a growing sense of ownership and resilience as a writer. However, the students encountered some challenges, such as the conflicts between the AaL training and the summative assessment requirement of the curriculum, as well as a lack of sustained teacher support in the assessment tasks. Implications on how to integrate AaL with L2 writing teaching in higher education contexts are discussed.