This paper deals with the relationships between the H-factor and the dissolving rates of main saccharides,the ratio of total saccharides and pentose to the total solid as well as the concentration of furfural（F） and hydroxymethylfurfural（HMF） in the hot-water preextracted liquor of bamboo in different conditions.The results show that（1） for the purpose of obtaining more saccharides and reducing the conversion of saccharides to F and HMF,the lgH value during the preextraction should be controlled within the range of 3.2～3.4,and the maximum preextraction temperature should not be higher than 160℃;（2） when the lgH value is lower than 3.2,the dissolving rates of saccharides decrease,while when it is higher than 3.4,some saccharides convert to F and HMF,and the dissolving rates as well as the ratio of total saccharides and pentose to the total solid decrease;and（3） at the maximum dissolving rate and the same H-factor,more saccharides may convert to F and HMF at a higher temperature（160℃）.