Abstract:Bombyx mori silk and spider dragline silk fibers have many advantages such as excellent mechanical properties, biocompatibility and biodegradability. This article describes the primary structure, secondary structure, β-crystal network (nanofibril) structure and the formation process of multi-level structure. The effects of the hydrophobic and hydrophilic domain, molecular weight and crystal network structure on the mechanical properties of silk protein fibers are reviewed. Among them, the strength of the crystal network is the key to the mechanical properties, which is determined by the four factors of topological structure, correlation length, degree of orientation and strength of the connection or interaction. The summary of these four factors provides guidance for the control and improvement of the mechanical properties.