Suicide is a major public health concern and there is a need for accessible and scalable interventions to support individuals experiencing suicidal thoughts. The aim of this study is to develop a digital Acceptance and Commitment Therapy (ACT) intervention for suicide prevention in Chinese adults through co-design. The study will involve literature review, interviews, and co-design activities to identify user needs, preferences, and contextual factors, and to develop the intervention. Following intervention development, a pilot study will be conducted to evaluate the feasibility, usability, acceptability, and user engagement of the intervention. Findings from this study will inform further refinement of the intervention and future evaluation studies.