Abstract: The silk fibroin(SF)/sodium alginate(SA) double network composite fiber was prepared by incorporating silk fibroin cross-linked with polyethylene glycol diglycidyl ether(PEGDE) as a cross-linking agent into sodium alginate cross-linked with CaCl₂ as a cross-linking agent. The apparent viscosity of spinning solution and properties of as-prepared crosslinking modified composite fiber were characterized by DV-C display viscosity meter, FTIR, Electronic single fiber strength tester, nuclear magnetic resonance temperature relaxation analyzer, SEM and XRD. The effects of cross-linking agent PEGDE content on the mechanical properties, micromorphologies, cross-linking degree, moisture absorption performance and preserve moisturizing performance of cross-linking modified SF/SA composite fiber were investigated in details.The results indicate that the apparent viscosity of spinning solution decreases first and then increases as the crosslinking agent is added; addition of appropriate amount of crosslinking agent can reduce the apparent viscosity of the spinning solution and increase the spinnability of the fiber; while it affects the breaking strength, the breaking elongation and the degree of cross linking in the opposite way. More specifically, the breaking strength and crosslinking degree both reach the maximum (2.34 cN/dtex and 55.8%, respectively), when the mass ration of crosslinking agent PEGDE and silk fibroin is 3:1. The higher the degree of crosslinking is, the more significant the trench structure on the surface of crosslinking modified SF/SA composite fiber is and the better for the compatibility of the composite fiber. In addition, hygroscopicity and moisture retention of crosslinking modified composite fiber has been improved and the moisture absorption equilibrium time is advanced.