Recent advances in solid superacids are reviewed. The acid stronger than H₀ = -11.93, which corresponds to the acid strength of 100 % H₂SO₄, is know as superacid. However, solid superacid catalysts have many advantages  such as an easy separation of products from catalyst, the repeated use and regeneration of catalysts, as compared with liquid superacids. The preparation methods, surface properties including acid amount and acid strength, structures of acid sites and the applications of solid superacid catalysts to several chemical reactions are presented.