Hydroxyapatite nanoparticles were prepared in low Ca/P ratio by a kind of electrodeposition-hydrothermal process. The suspension of nanoparticles was cultured with SGC-7901 cells; metabolically active cells were evaluated by MTT analysis. Cells grew well and the nanoparticles in the concentration range of 10-100 microg/ml had no adverse effect on the cell viability. The results show that the nanoparticles have excellent biocompatibility with cells. Agrose gel electrophoresis analysis demonstrated that the nanoparticles had the potential to adsorb EGFP-N1 at the pH ranging between 2 to 7. Nanoparticle-DNA complex could transfer EGFP-N1 into the SGC-7901 cells, and the confocal microscopy analysis revealed that the cells with green fluorescence showed the efficiency of nanoparticle uptake to be about 80% of the efficiency of the Lipofectmine TM 2 000 uptake. In vivo, nanoparticles and DNA-nanoparticle complex were injected into mice respectively via tail-vein, and the mice grew well in two weeks. The liver, kidney, and brain of the mice were sampled and detected with electron microscopy, and all of these exhibited biodistribution of nanoparticles. This study demonstrates that Hydroxyapatite nanoparticles could be used as gene carriers.