In this article, tensile behaviors of polyamide 6 and polyolefin blends were studied. Differential scanning calorimeter (DSC) was used to investigate the melting behaviors of injection-molded specimens and corresponding post-tensile tested specimens. As a result, the content of polyolefin blend, water, and anneal time has strong incidences on tensile behaviors of polyamide 6 blends. Double yielding was found in several blends under different conditions. DSC results showed that there are changes of crystal structure during tensile deformation. Finally, the origin of double yielding is detected to be related to polyamide 6.