<p>In this paper, long carbon chain bio-based semi-aromatic polyamide PA9T, PA10T and PA12T were synthesized by using bio-based monomers nonenediamine, decamethylene diamine and dodecane diamine as raw materials. Materials studio software, universal testing machine, impact testing machine and other software and instruments were used, the physical and chemical properties of PA9T, PA10T and PA12T were studied in detail from both micro and macro perspectives. The results show that in the single-molecule model, PA12T exhibits the largest Poisson’s ratio, but the smallest bulk modulus, shear modulus, and Young’s modulus; PA9T shows the opposite trend, while PA10T is intermediate between the two, indicating that the less methylene in the single molecule model, the better the mechanical properties. From the macroscopic point of view, with the increase of methylene content, the tensile strength and bending strength decreased, while the elongation at break and the impact strength increased. The density also showed a gradual decreasing trend, and the oil absorption rate and water absorption rate gradually decreased. At the same time, with the increase of carbon chain, the solvent resistance is gradually enhanced, and the performance retention rate is gradually increased.</p>