Abstract: The hexa-poly(amino acids) and tetra-poly(amino acids) based on 6-aminohexanoic acid were synthesized by in-situ melting polycondensation. In vitro bioactivity of hexa-poly(amino acids) and tetra-poly(amino acids) were characterized in comparison with polyamide and polyethylene. Fourier Transform Infrared Spectoscopy (FT-IR)、X-ray Diffraction (XRD)、Differential Scanning Calorimetry (DSC) and Thermal Gravity (TG) analysis of hexa-poly(amino acids) and tetra-poly(amino acids) were characterized for evaluating their chemical features. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) of hexa-poly(amino acids)、tetra-poly(amino acids)、polyamide and polyethylene were tested after soaking into simulated body fluid (SBF) for 5 d for assessing apatite forming in their surface. Results showed that hexa-poly(amino acids) and tetra-poly(amino acids) possessed amide band were both semi-crystallization structure. Peak crystallization temperatures of hexa-poly(amino acids) and tetra-poly(amino acids) were 159.5℃ and 157.6℃, respectively. Melting temperature of hexa-poly(amino acids) and tetra-poly(amino acids) were 205.9℃ and 204.4℃, respectively. The total mass loss of tetra-poly(amino acids) and hexa-poly(amino acids) were 98.5% and 98.0% at about 800℃, respectively. SEM and EDS results showed that hexa-poly(amino acids) and tetra-poly(amino acids) induced the form of apatite on their surface after soaking into SBF for 5 d, showing good bioactivity. However, polyethylene and polyamide were not bioactive. w(Ca)/w(P) for hexa-poly(amino acids) and tetra-poly(amino acids) were 2.58 and 2.94, respectively.