Critical bone defect repair remains a major challenge in orthopedic. Cynomorium songaricum polysaccharide (CSP), derived from the traditional medicinal plant Cynomorium songaricum Rupr in China, demonstrates excellent anti-inflammatory and osteogenic properties. Given these promising biological activities, we developed a novel therapeutic approach using a hydrogel composite scaffold incorporating CSP (GAC-C) for treating critical-sized bone defects. The composite scaffold was fabricated by embedding CSP into the methacrylated gelatin (GelMA)/sodium alginate(SA)/carboxymethyl chitosan (CMCS) blend via 3D printing technology. The structural, mechanical, and biological properties of GAC-C were characterized, and osteogenic performance was evaluated both in vitro with rat bone marrow stromal cells (rBMSCs) and in vivo using a critical-sized bone defect model. Results showed that the GAC-C scaffold demonstrated excellent biocompatibility, promoted osteogenic differentiation of rBMSCs, and enhanced bone integration and repair. Thus, the GAC-C scaffold shows potential for effectively repairing critical-sized bone defects.