Pancreatic cancer is a highly aggressive malignancy often associated with severe malnutrition, which compromises treatment tolerance and clinical outcomes. CyberKnife radiotherapy is an effective treatment for inoperable tumors, but can still impact patient's nutritional and immune status. While nutritional support is critical, a systematic, phased approach guided by risk screening is not well-established in this patient population. This single-center, prospective, randomized controlled trial was designed to address this gap. A total of 100 patients with pancreatic cancer and malnutrition (NRS2002 score ≥3) were randomly assigned to either a study group or a control group. The control group received routine dietary education. The study group received a comprehensive sequential nutrition intervention managed by a multidisciplinary team. This intervention included initial nutritional risk screening, tailored energy and protein targets calculated using the Harris-Benedict formula, a phased protocol for nutritional support before and after CyberKnife treatment (including oral nutritional supplements, enteral, and parenteral nutrition as needed), and continued post-discharge follow-up. The hypothesis is that this structured, sequential approach will significantly improve nutritional biomarkers, enhance immune function, lead to a better quality of life, and decrease complications compared to routine care.