Abstract: In order to make clear of the crystallinity change characteristics of moso bamboo in different heat pretreatments, improve the treatment processing and the development and utilization technology of bamboo base composite material, the changing rule of the crystallinity of four-year raw bamboo was studied under the 117 and 135 ℃ with different concentration of acid, alkali and glycerol. The pretreated bamboo samples were filtered through a Buchner funnel and washed with deionized water until the effluent was pH-neutral, and then dried in the oven for 1 h at(103±5) ℃. Extractives in the samples were removed by Soxhlet extractor for 12 h with 80 mL ethanol and 40 mL benzene. The extracted residue was air-dried overnight prior to characterization. Holocellulose was isolated from extractive-free biomass using a modified procedure from the literature. Extractive-free pretreated samples(2 g), deionized water(150 mL), sodium chlorite(1.0 g) and glacial acetic acid (0.2 g) were added into a kapak sealing pouch, and the sealing pouch was in a shaking water bath for 1 h at 75 ℃. After 1 h, another batch of sodium chlorite and glacial acetic acid were added and the mixture was heated in the water bath for 1 h again. This process was repeated 4 times until the holocellulose turned white. Then, the pretreated bamboo samples were cooled, filtered through a Buchner funnel, washed several times with deionized water and air-dried in a fume hood. Cellulose was isolated from holocellulose sample by an acid treatment following a procedure from the literature that holocellulose was treated with 17.5% NaOH (50 mL) at 98-100 ℃ for 4 h, cooled to 0 ℃, filtered in a Buchner funnel, washed several times with deionized water and air-dried in a fume-hood. The methods included using crystal X-ray diffraction to measure the area length, spacing, crystal plane diffraction peak position, crystalline index and parameters, using scanning electron microscopy (SEM) to verify the change of crystalline region, and using thermo gravimetric analysis(TGA) to complete the thermal degradation studies for moso bamboo. Results showed that the 002 peak position in the direction of large angle was obviously offset, the 002 crystal width and the grain size in crystalline region were decreased, and the half peak width in crystalline region was becoming smaller. In addition, its high peak deformation was sharp, and the crystalline intensity increased significantly after different chemical heat treatment; the trend of relative crystallinity declined at 117 ℃, and when the temperature rose to 135 ℃, it recovered gradually. SEM and TGA further validated that the fibrous structure became thinner and there was the tendency difference for pyrolysis temperature of chemical compositions after processing; a comprehensive study showed that after treatment the cellulose content was increased, the lignin removal effect was obvious, and the chemical composition of several different processes had a relatively large difference. Research results will provide the theoretical reference basis for the regeneration and processing of bamboo and the development and utilization of bamboo base composite.