Abstract: Hydroxyapatite (HAP) nanofibers with ultra-high aspect ratio were prepared by a solvothermal method. HAP nanofibers reinforced composite hydrogel combined with gelatin modified by methacrylic anhydride(GelMA) was prepared by UV crosslinking. The composite hydrogel was characterized by SEM, XRD, mechanical test, swelling test, degradation test and cell culture, etc. The results of the cross-sectional morphology show that the HAP fiber/GelMA composite hydrogel has 3D porous structure with porous structure. Mechanical experiments show that HAP nanofibers can effectively enhance the elastic modulus of the composite hydrogel. With the increase of HAP nanofibers addition, the mechanical performance enhancement effect of the HAP/GelMA composite hydrogel is more obvious. The swelling experiments show that the swelling rate does not change significantly when the mass fraction of HAP fiber is 5.2wt%-14.2wt%, while the swelling rate decreases when the mass fraction is 18.2wt%. The degradation experiments show that the addition of HAP nanofibers can effectively maintain the structure of hydrogel and make it more stable and controllable. The cell co-culture experiments show that the HAP nanofibers/GelMA composite hydrogel can provide a great 3D growth environment for encapsulated cells, showing excellent biocompatibility. The HAP nanofibers/GelMA composite hydrogel prepared in the experiment has a good application prospect in the field of tissue engineering.