Abstract: To regulate carbohydrate reaction in the poplar autohydrolysis of biorefining, the effects of different P-factors on the pH value, hydrolysis rate, reducing sugar, holocellulose, different monosaccharides and furfural product in the poplar autohydrolysis system were studied in detail. The results showed that with the increase of P-factor to about 2 800, the pH value of the system decreased continuously to 3.6, the total hydrolysis rate and holocellulose removal rate reached 47% and 54%, respectively. Arabinose and rhamnose in pentosan were almost completely hydrolyzed, xylan was mostly hydrolyzed, and the removal rate of glucan was 37%(mostly from hemicellulose). The trend of total hydrolysis, holocellulose removal and pentosan removal could be divided into a fast and a following slow removal phase in the process. There was a positive correlation between P-factor and furfural production, which could be divided into a slow and a fast phase, and the conversion of pentose to furfural was 40%. P-factor could regulate the autohydrolysis of carbohydrate in poplar.