Design: Parallel-arm RCT with 40 participants (20 in each group). Participants are randomly assigned to either the intervention group (mobile-based mindfulness intervention + usual care) or control group (usual care only). The intervention uses a free and anonymous mindfulness mobile app developed by The University of Hong Kong. Primary Outcome: Preoperative anxiety level on the day of surgery, will be assessed using the STAI-S questionnaire. Secondary Outcomes: Postoperative pain levels, use of analgesics, emergency department revisit rate, and user satisfaction with the app. Data Collection: Anxiety levels are measured at baseline and before surgery. Pain levels and analgesic use are recorded postoperatively. Emergency visits and usability feedback are collected post-discharge. Significance: The study addresses a gap in evidence for mobile mindfulness interventions in Chinese surgical patients. Findings may support the integration of low-cost, app-based mindfulness into preoperative care.