The invention discloses a chemical crosslinking modified silk fibroin/alginate complex fiber and a preparation method of the chemical crosslinking modified silk fibroin/alginate complex fiber. The chemical crosslinking modified silk fibroin/alginate complex fiber is prepared by extracting silk fibroin from a silkworm cocoon, mixing an extracted silk fibroin solution and a sodium alginate solution, adding a crosslinking agent for chemical crosslinking reaction, and performing wet spinning on a spinning solution after the reaction. Mechanical properties of the chemical crosslinking modified silk fibroin/alginate complex fiber are greatly improved; and in a preparation process of the chemical crosslinking silk fibroin/alginate complex fiber, the quantity of crosslinking points of the crosslinking agent and the silk fibroin, and a crosslinking degree can be controlled by changing the content of the crosslinking agent, so that the balance between fiber strength and spinning solution processability is adjusted to meet requirements for actual processing and application.