Three poly(n-alkyl acrylates), PA-14, PA-16, and PA-18, and three poly(vinyl alcohol) aliphatic acid esters, PVA-14, PVA-16, and PVA-18, have been synthesized. They are white crystalline polymers at room temperature and characterized by IR, DSC, SALLS-photometer, and polarizing microscope. Both the melting point and heat of fusion of PVA–esters are larger than those of the corresponding PA–esters, and the sizes of spherulites of PVA–esters are also larger. This may be attributed to the different order of linking in the ester group and the OH group residue in PVA–esters. In the testing of the effects on pourpoint depression of some petrolic oils, only PA-14 and PVA-14 are effective for 0# diesel oil. The influences of molecular weight and molecular weight distribution of PA–esters and PVA–esters upon the pour-point depression of oil are negligible. These results show that the length of n-alkyl side chain of the polyesters plays the most important role in depressing the pour-point of petrolic oil and that the order of linking in the esters group seems to be in no relation to this effect.