Abstarct: Abstract: Treatment of bone defects is one of the most complex issues in orthopedic surgery. Although the bone tissue of living organisms can be used in transplants,but problems such as organ donor deficiency, incompatibility of the donor organ with the host body, and other problems have led to the use of biocompatible synthetic materials.Therefore, in this study, the chemical and physical properties of this nanocomposite were investigated by synthesizing a bioactive hydroxyapatite-alginate-carbon quantum dots nanocomposite. The synthesis of this nanocomposite was performed in situ. Carbon quantum dots were synthesized using citric acid precursor and then these dots were added to the composition during the synthesis of hydroxyapatite-alginate. In this study, apatite Created with co-precipitation technique directly on alginate co-polymers.The optical and chemical properties of carbon quantum dots and nanocomposites were investigated by UV-visible spectroscopy spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR) and photoluminescence (PL). Their thermal behavior was also investigated by Thermogravimetric analysis (TGA). phase and nanoparticle morphology studies were performed by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) with EDS, respectively. FTIR spectroscopic analysis confirmed the presence of C=C bonds at carbon quantum dots and (O-P-O), (-COO-), (-COOH) in nanocomposites. Carbon quantum dots have two absorption peaks at 230 nm and 360 nm. By excitation of carbon quantum dots at wavelengths of 200-400 nm, the emission spectrum is obtained, which increases with the excitation wavelength, the peak of the emission spectrum shifts to longer wavelengths.The results of TGA showed the two weight loss peak in nanocomposite. This peaks attributed to the removal of adsorbed physical water, carbon burning, decomposition of dihydrates in hydroxyapatite, and rupture of chains, parts, and monomers in alginate. XRD results showed the formation of hydroxyapatite phase in the synthesized samples. FESEM analysis showed that a complete and unified composite structure was formed. FESEM observations showed synthesized rod-shaped nanocrystals of hydroxyapatite.The images of the nanocomposites showed the cohesive texture formation . good dispersion of the elements, and especially the good dispersion of carbon showed by EDX, which confirms the proper bonding and settling of these particles in the composite.