Calcium and hydroxyproline dissolving amounts were used as evaluation index to study the effect of hydrochloric acid decalcification on fish scale.The results indicated that hydrochloric acid with low concentrations could improve the hydroxyproline dissolving amounts.With the increment of hydrochloric acid concentrations,pickling time and solid-liquid ratio,the calcium dissolving amounts were increased significantly at first and then became stable.The surface structures of scales before and after decalcification was compared.The results showed that scales without decalcification were rough white due to adhesion of hydroxyapatite.However,scales with decalcification were transparent and had a prominent network structure which would be favorable for collagen extraction later on.