The effect of polar monomer styrene content on the effectiveness of the performance of poly(octadecyl acrylate) (POA) pour-point depressant (PPD) was studied using the model waxy oils (MWOs) and Shengli crude oil. A set of controlled styrene content was copolymerized with octadecyl acrylate to make poly(octadecyl acrylate-styrene) (POA-S). The performances of POA and POA-S in MWOs and Shengli crude oil were evaluated by measuring their ability to decrease pour points of model waxy oils and waxy crude oil. It was found that when poly(octadecyl acrylate) and styrene monomer mole ratio was 3:2 the PPD gives optimum performance in MWOs and Shengli crude oil. After POA-S was added to MWO1, MWO2, and Shengli crude oil, the pour points could be reduced by as much as 32, 31, and 19 degrees C, respectively. The result illustrated that the presence of POA-S in the MWOs, crude oil, and paraffin wax affects the crystallization process, leading to the wax appearance temperature (WAT) decrease in each test. Differential scanning calorimetry (DSC) test showed that the wax crystal phase transformation can occur after POA-S has been doped in MWOs and paraffin wax; the exothermic peak is also split into a doublet. The crystallization performance of paraffin wax was investigated by X-ray diffraction (XRD). The increase in the distance between visible platelet-like wax crystals is observed by scanning electron microscopy (SEM). This result gave reasonable proof in improving the flowability of the MWOs by POA-S.