This project employs a prospective, double-blind, randomized controlled trial methodology to comparatively analyze the safety and survival outcomes of human umbilical cord blood RAK cells applied in advanced gastric cancer. Firstly, the maximum tolerated dose (MTD) of RAK cell therapy for patients with advanced gastric cancer will be determined through a dose-escalation trial. Subsequently, the overall survival (OS), progression-free survival (PFS), and incidence of adverse events will be compared between the RAK treatment group and the control group. This aims to explore the efficacy and safety of biotherapy for recurrent or metastatic gastric cancer where frontline therapy has failed, thereby laying the foundation and providing evidence for large-scale, multi-center clinical studies.