In this investigation, multi-wall carbon nanotubes (MWCNT) with various percentages (0.6%, 1%, 1.4%, 2%) were combined into and High-density polyethylene HDPE (60) wt. % and hydroxyapatite (40) wt. % to form biocomposite using hot-press techniques. The surface topography by AFM images illustrates differences in the roughness of the sample's surface with different adding percentages of MWCNT. The DSC technique exhibits the effect of adding MWCNT in different percentages with the degree of crystallinity, which its effect on mechanical properties for samples. The in vitro bioactivity was investigated by immersion the samples in Ringer's solution as simulated body fluid (SBF) at (0, 3, 6, 9, 12) days (after immersing). The FE-SEM and EDx image explained the apatite layers formation on the sample's surface after 3 days immersed in Ringer solution. Based on XRD Technique, after immersion days in the Ringer solution, the crystallographic structure of hydroxyapatite is formed, forming the monetite. The enhancement of bioactivity has been shown during the incorporation of MWCNT into HA/HDPE composite. These results exhibited excellent indications of biocompatibility properties with the possibility of making promising biomaterials for making bone substitute applications.