A series of environmentally friendly polyamides (PA69, PA109 and PA129) have been synthesized by carrying out step-melting polycondensation reactions of bioderived monomers: 1,9-azelaic acid with different chain length diamines, respectively. Their molecular structure and chemical composition have been characterized using elemental analysis (EA), Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (H-1-NMR) spectroscopy. Their crystal structures, mechanical properties, thermal behaviors and moisture absorption properties have also been investigated. The number-average molecular weights of PA69, PA109 and PA129 were 51,300, 38,900 and 38,500, respectively, and the main crystal structures of them were alpha-crystalline and gamma-crystalline form. As the length of diamine increased, the melting temperatures of them were from 214 to 203 to 195 degrees C, respectively, and the crystallization temperatures of them were from 176 to 166 to 161 degrees C, respectively. The bending strengths of them were determined to be 102.58 MPa, 84.11 MPa, 65.91 MPa, respectively, and the izod impact strengths of them were 9.24 kJ/m(2), 8.82 kJ/m(2), 8.54 kJ/m(2), respectively. They were also found to absorb less moisture than PA6 and PA66.