Abstract: In order to increase the wheat straw lignocellulose energy-oriented use efficiency,the technology optimization of pretreatment of wheat straw by propionic acid under mildness condition was studied. The experimental results showed that the optimum working conditions were as follows: materials to liquid ratio 1:16, particle size 40 mesh, propionic acid concentration 900 g/L, catalyst concentration 3 g/L, temperature 70℃, pretreatment time 150 min. The remaining rate of cellulose of wheat straw was 92.6% under the optical conditions，and the elimination rates of hemi-cellulose and lignin of wheat straw after propionic acid treat ment were 98.3% and 70.5% respectively.The enzymatic hydrolysis yield of wheat straw pretreated by propionic acid was 90.3%.Under mildness condition,wheat straws pretreated by propionic acid were degraded into the three parts, cellulose, hemi-cellulose and lignin.