The polyamide 6 (PA6)/K resin (K) blends of some kinds of compositions have been prepared by extrusion. During the process of tensile testing, we found that the PA6/K blend with 10% PA6 has the usual stress-strain behavior, and that the samples obtained with 30% and 50% PA6 show apparently double yielding behavior, while the PA6/PS blend does not show the double yielding phenomenon at all same mass ratio. Considering the microscopic morphology study and results of mechanical properties of the PA6/K blends, the first yield point which occurs at the lower tensile stress might be caused by the deformation of the K resin matrix, and the second one may be correlated to the permanent plastic deformation of the entanglement of PA6 chains and PB segments within chains of K resin.