Objective To study the inhibitory effect of sodium alginate on tyrosinase and melanin production. Methods Enzyme inhibition kinetics experiment was carried out. The inhibitory effect of sodium alginate on tyrosinase activity was analyzed by fluorescence spectroscopy, and the inhibitory effect of sodium alginate on melanocytes was studied. Results Sodium alginate could significantly inhibit tyrosinase activity. When the concentration of sodium alginate was less than 20 mmol/L, the higher the concentration, the better the inhibitory effect. More than 20 mmol/L, the inhibition rate of sodium alginate on tyrosinase activity was 65.45%. With the increase of sodium alginate concentration, the inhibition rate of intracellular melanin production increased, and the melanin production decreased. The interaction between sodium alginate and tyrosinase was destructive to the hydrophobic environment of amino acid residues, resulting in the red shift of endogenous fluorescence spectra. Sodium alginate had no obvious toxicity to melanocytes with the activity of more than 90%. Conclusion Sodium alginate can be used in the treatment of skinrelated diseases and whitening cosmetics, and the effect is good.