In order to ensure the safety of low-temperature flow in long-distance pipeline transportation of offshore crude oil, a ternary copolymer was synthesized using octadecyl acrylate, octadecene, and styrene as monomers. The polyolefin pour point depressant and wax inhibitor POOS was synthesized using it as the main agent. The synthesis conditions of the ternary copolymer were optimized, and the rheological properties, wax precipitation characteristics, microstructure, and pour point and wax reducing and preventing effects of the crude oil before and after the addition of the agent were evaluated. The results showed that the optimized synthesis process conditions for the copolymer were as follows: monomer molar ratio n(octadecyl acrylate): n(octadecene): n (styrene)=5:3:2, initiator benzoyl peroxide mass fraction 5 ‰, reaction temperature 70 ℃, and reaction time 8 hours. When the mass concentration of POOS is 200 mg/L, the rheological properties of crude oil show significant changes compared to non POOS crude oil. At 15 ℃, the yield stresses before and after adding the agent are 50.3 and 2.95 Pa, with a decrease of 94 % in yield stress. The wax precipitation temperature drops from 31.33 ℃ to 24.94 ℃, the pour point drops from 25 ℃ to 15 ℃, the cold index test shows a wax prevention rate of 88 %, and the ring test shows a wax prevention rate of 83.7 %. Microscopic analysis shows that the wax crystal morphology changes from needle shaped to circular shaped, and the precipitation distribution is uneven, Multiple small wax crystals aggregate and precipitate to form a single aggregate. Adding additives effectively improves the dispersion morphology of wax crystals, inhibits the formation of network structures, and significantly improves the low-temperature flow effect of crude oil.