Rattan is an important non-timber forest product inferior to timber and bamboo, with high economic value and development prospects. But little is known about the cell structure of rattan, especially the cell wall structure of fiber at present, which seriously limits the research, processing and utilization of rattan. Therefore, in order to construct the fiber wall structure model and explore the toughness mechanism of rattan, Plectocomia himalayana was chosen as the research material, and X-ray diffraction (XRD) was used to calculate the microfibril angle (MFA), crystallinity and size of microcrystals, among them 0.4T method was used to calculate the MFA. In the MFA test, eight specimens with the size of L(long)×T(thick)×W(wide)=25 mm×0.5 mm×W were selected from one side of the cortex in turn along the diameter direction of the sample, and then placed in the Temperature and Humidity Control Box with the temperature of (20±2)℃ and the relative humidity of 65%±5% for at least one week. When measuring crystallinity and microcrystalline size, each sample was divided into the cortex, middle layer and core. After grounding into powder by Ball Mill, it was put into the Oven and dried to absolute drying at (103±2)℃. The results showed that: the MFA of P. himalayana varied from 22.53° to 49.47° with an average of 36.50°. The MFA was the smallest in the cortex and the largest in the core in radial, which indicated the strength of cortex was better than that of the core. The MFA was 2 m>the tip>the middle>the base in axial, and the regularity between the MFA and the rattan age was not obvious. The cellulose crystallinity varied from 21.40% to 36.45% with an average of 29.99%, and the cellulose crystallinity was the cortex>middle layer>core in radial. Axial upward, with the decrease of rattan age, the crystallinity increased first and then decreased and the maximum value was in the middle and the minimum value was at the base. The microcrystal width of cellulose varied from 5.72 to 6.19 nm with an average of 6.03 nm. The average width of microcrystals at cortex was the smallest and the core was the largest. Like the middle layer and core, the average width of microcrystals of rattan stem decreased first, then reached the minimum in the middle and then rose with the increase of the height. The microcrystal length varied from 13.07 nm to 19.34 nm with an average of 15.59 nm. The length of microcrystals was the cortex>core>middle layer in radial; the length of microcrystals showed a downward-upward-downward trend along with the increase of rattan height in axial, and the microcrystal length at the base was higher than that at the tip, showing a downward trend. The middle part of the stem is better than the base part and the tip part, and the cortex is better than the core.