Abstract: The experiment took wheat straw as the pretreatment object to study the effect of hydrogen peroxide and lime combined pretreatment with different concentration ratio on the content of cellulose,hemicellulose and lignin (three elements) in wheat straw and the effect of different pretreatment time on the content of three elements in wheat straw.The effects of freezing-thawing conditions on the content of three elements in wheat straw were also investigated.Use titration method to determine three content,through research to determine the optimum freeze-thaw combined alkali pretreatment conditions as followsWhen the mass fraction of hydrogen peroxide and calcium hydroxide was 0.4% and 0.2% respectively after two days of freezing at -10 ℃ and melting at100 ℃,the content of tri-element in wheat straw decreased most obviously,including17.5% cellulose,6.8% hemicellulose and7.8% lignin.

Key words: wheat straw, freezing and thawing, alkali, combined pretreatment