The cryopreservation of cells, tissue, and organs is essential in both fundamental research and practical applications, such as modern regenerative medicine and technological applications. However, the formation of ice crystals during ice recrystallization can have harmful or even fatal effects on biological systems. To address this challenge, we explore the ice recrystallization inhibition (IRI) activity of two natural silk proteins of Bombyx mori, fibroin and sericin. We found that silk fibroin (SF) had higher ice recrystallization inhibition activity than silk sericin (SS). Moreover, SF aqueous solutions perform better in inhibiting ice recrystallization than SF phosphate-buffered saline solutions. Sum-frequency generation spectroscopy shows that stronger electrostatic interactions are responsible for the higher IRI ability of SF. This work is significant for broadening the applications of silk proteins in biomedical fields.