Abstract: Highly oriented polyamide 6 (PA6) was successfully fabricated through solid hot stretching technology. The effect of orientation on the structure and hygrothermal stability of PA6 was investigated. It was found that with the increase of draw ratio, the crystallinity and orientation factor of PA6 increased, and micro-fibre structure was formed, while the hydrophilic property was weakened. During hygrothermal aging, the equilibrium water absorption ratio and water absorption rate of PA6 decreased with the increase of draw ratio, and the oriented samples kept relatively higher reduced viscosity and mechanical property. The surface cracks appeared during aging and remarkably reduced by orientation. The fractional free volume, the crystallinity and crystal form of the oriented samples also kept to be relatively stable. The enhancing mechanism of hydrothermal stability of PA6 was studied. ACKNOWLEDGEMENTS This work was supported by the Key Natural Science Fund of China (51133005).