This study developed a dietary polysaccharide-stabilized peptide-Fe²⁺ composite beverage to address iron deficiency anemia (IDA). Through single-factor and orthogonal experiments, the formulation was optimized (cranberry/blueberry concentrate ratio 4:6, 600 mL/L; FA-COS@Peptide-Fe²⁺@PTry-CMC 200 mL/L; vitamin C 1.5 g/L; pectin 0.06 g/L), and processing parameters were determined (homogenization: 12,000 rpm, 20 min; sterilization: 95 °C, 15 min). Storage stability was optimal at 4 °C in dark conditions. Under the optimal processing conditions, the beverage attained a maximum suspension stability of 17.74% and the optimized formulation achieved a highest sensory score of 94.0 (out of 100). In vivo experiments showed that the beverage dose-dependently restored hematological parameters (e.g., HGB, SI, TIBC) and tissue iron levels, alleviated intestinal oxidative stress and inflammatory markers in IDA mice, while repairing colonic mucosal damage without adverse effects. The beverage demonstrated high iron-supplementing efficacy and excellent biosafety, offering a promising strategy for IDA intervention.