The partially disentangled poly(vinyl chloride) (PVC) samples were prepared by freeze-extracting from dilute PVC/THF solutions. The conformation of these samples was investigated by infrared and Raman spectroscopy. The structural relaxation behaviors were studied by differential scanning calorimeter (DSC). The results showed that the PVC samples prepared from dilute solutions with concentrations lower than 0.25% were in the expanded state with fewer entanglements. The conformation and structural relaxation of PVC depended strongly on the entanglements in polymers, and the structural relaxation rate increased with decreasing chain entanglements, which is in good agreement with the modeling predictions.