Abstract: Saccharum spontaneum L., which is a high-yield cellulose, is noticed as an energy plant at presentall over the world. The acid hydrolysis and saccharifying of straw is a key process in the fuel ethanol production. Inorder to solve the problem with low yield of acid hydrolysis and saccharifying in the technique of producing ethanolfrom biomass, by single factor orthogonal test, the process conditions of normal pressure two-stage acid hydrolysisare optimized as follow: the first section was concentrated sulphuric acid hydrolysis in 70% sulphuric acid at 55 for 20 min, and the ratio of liquid to solid was 421; the second section was dilute sulphuric acid hydrolysis in 5.5%sulphuric acid at 100for 155 min, and the ratio of liquid to solid was 1151. The yield of reducing sugar was48.78% in two-stage hydrolysis. The technology of two-stage acid hydrolysis has advantages of moderate condition,simple flow, low pressure, low cost, high reducing sugar yield and broad application prospect. The results may be thebase of utilization of S. spontaneum L.