The work aims to prepare hydroxypropyl nano-cellulose/hydroxyapatite (NCC-HPC/HA) nanocomposites. The surface of nano-cellulose (NCC) was chemically modified with propylene oxide as modifier to obtain surface modified nano-cellulose (NCC-HPC) to improve the surface hydrophobicity and dispersion of NCC. On this basis, NCC-HPC/HA nanocomposites were prepared by co-precipitation method with NCC-HPC as nucleation point, and the structure and properties of the composites were studied. Hydroxyapatite nanospheres were successfully synthesized on modified nanocellulose by co-precipitation method. It was confirmed by analysis that the NCC surface modified by propylene oxide had almost no crystal structure change, its hydrophobicity and redispersion were improved, and it could stably exist in water and other organic solvent systems. The contact Angle between NCC-HPC and water increased from 17° to 55.3°. The surface of NCC-HPC/HA nanocomposite was uniformly distributed with Ca and P elements, and the Ca/P ratio was 1.64, which was close to the Ca/P ratio of real bone. The mechanical properties of the composites pressed at 2 MPa showed that:Compared with the NCC without surface modification, the mechanical properties of NCC-HPC/HA nanocomposites prepared by surface modification of nanocellulose were improved. The tensile strength could reach 3.48 MPa, an increase of 6.7%, the bending strength could reach 5.22 MPa, an increase of 4.4%, and the compression strength could reach 2.11 MPa. That‘s a 4.7 percent increase. The hydrophobicity of NCC modified by hydroxypropyl was improved, and its dispersion in aqueous solution was obviously improved. It was due to the introduction of new groups on the surface of NCC, which made the surface of particles become fluffy, particles were not tightly stacked, and the adsorption between particles was greatly weakened. The spherical nano-hydroxyapatite (n-HA) in the NCC-HPC/HA composite prepared on this basis was uniformly distributed on the linear NCC-HPC, which had good mechanical properties and thermal stability, and was suitable for bone tissue engineering applications.