The object of the present paper was researching a kind of nano cellulose prepared by the pretreatment of diluted acid and the physical method of high pressure homogenization.The cellulose pulp was pretreated by diluted acid and then prepared by high pressure homogenization.The one-dimensional rodlike nano cellulose was obtained.And the spectral properties of nano cellulose were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).The thermal property of nano cellulose was analyzed by thermogravimetric analysis (TGA).The dimension and morphology of nano celluose were observed using atomic force microscope (AFM) and transmission electron microscopy (TEM).FTIR analysis results showed that the one-dimensional rodlike nano cellulose had the same characteristic functional groups as cellulose pulp.And it was showed that intramolecular hydrogen bond association effects of nano cellulose were partly destroyed.It was indicated by XRD analysis that nano cellulose and cellulose pulp corresponded to the crystal type of cellulose Ⅰ.The crystallinity of nano cellulose was increased from 59% to 70%, compared to cellulose pulp.Nano cellulose still maintained both crystalline domains and amorphous regions, although crystalline domains and amorphous regions were partly damaged by preparing process.Thermal analysis results demonstrated that the thermal stability of nano cellulose was lower than that of cellulose pulp.The decomposition temperature of nano cellulose was 330 ℃.Two weight-loss stages were present in the range 292～500 ℃.The TEM photograph showed that nano cellulose was significantly rodlike shape with hundreds of nanometer in length and tens of nanometers in width.AFM image showed that nano cellulose was agglomerated together.