This paper deals with the study of extensibility of netting yarnsmade of Yilun folded monofilaments under the load below its breaking strength. Theextensible charateristic of these netting yarns includes elongation, toughness andelasticity. The results of experiment are as follows: 1. By breaking test, the elongation value of Yilun monefilament netting yarnsof the weaver's knot and the straight (knotless) acted under half knot breakingstrength is obtained. 2. The toughness and coeffecient (Q) by load-elongation curves were obtainedfrom breaking tests and by the insert value procedure of natural spline function. 3. The dergee of elasticity at various relaxed time is obtained by the elasticitytests under fixed elongation, then to get the relationships among the degree ofelasticity, diameter and relaxed time of the Yilun monofilament netting yarns.