The large diameter monofilaments were produced while the PA6/PA66 copolymers were used as raw materials.The properties of the large diameter copolymerization PA monofilaments after stretching were studied.The influence of stretching temperature,the stretching way,the stretching ratio and its distribution on the mechanical properties of the monofilaments was also studied.The structure of the copolymerization PA monofilaments was analyzed and compared with that of the similar homopolymer.The influence of mould stretch and normal stretch on the property of copolymerization polyamide(COPA) monofilament was studied.The result shows that: during the post-drawing,the best ratio of two-stage stretching is 4.7,the one-stage stretch percent is 85%,the temperature of hot water stretching is 90 ℃,and the temperature of hot air stretching is 180 ℃.