Abstract: The article comprehensively summarizes unconventional acidizing fluid compared to mud acid in sandstone formation, including fluorin boric acid, phosphoric acid, nitric acid, 5H⁺ acid, flio-silicic acid, sequential mud acid, in-situ generation of HF, buffer-regulated hydrofluoric acid systems, alcoholic mud acid, and mud acid plus aluminum chloride for retardation. The principles, characteristics and the application of various acidizing fluid system have been discussed in various degrees in the paper.