Voice in writing may be understood as a continuum of discursive and non-discursive features as constructed and negotiated between individual choice and social-cultural convention. It is increasingly acknowledged as a key indicator of successful academic writing. Current studies show that voice can be approached in L2 writing and assessed with reference to some key linguistic features. Assessment of voice in L2 writing is yet scarce largely due to the elusive nature of the concept and its partially controversial role and functions in diverse writing contexts. The assessment as learning (AaL) approach arises as a particular fit for assessing the significant yet somewhat controversial function of voice. Treating AaL as a holistic and unitary concept, the present student-centered assessment of voice construction is approached mainly via four steps: construct conceptualization, analysis of typical classroom writing and curriculum context, item design and development, and assessment cooperation among teachers and students. Firstly, we conducted a rigorous synthesis of existing literature to specify the definition of voice in academic writing and identified typical voice features in L2 learners’ academic writing. Literature review research was conducted with reference to theoretical frameworks related to voice, stance, evaluation, writer identity, and meta-discourse studies. A special attention was given to study on Chinese L2 learners’ voice features. Secondly, we conducted text analysis of target students’ writing, together with close examination of their curriculum expectation, classroom context and some classical academic writing monographs and textbooks. Typical principles were subsequently proposed in assessing students’ voice construction. Thirdly, guided under the principles of assessment as learning in integration with nature of voice, we designed and developed the assessment items with three main purposes: listening for voice, trying producing voice and learning to regulate voice. The items were student-essay-based and partly derived from students’ authentic writing, aiming at eliciting L2 learners’ knowledge, skills and strategies in voice construction. Finally, the assessment and evaluation process were implemented in the target classroom setting; and corresponding assessment criteria were negotiated and developed through teacher-student interaction, peer share, and self-evaluation. Overall, these four major steps of student-centered assessment activities and the anticipated generation of a set of assessment items and its companion assessment criteria are expected to provide individual learners with meaningful and useful criteria and feedback so as to facilitate development of students' disposition and skills to negotiate an effective authorial voice in L2 writing.