An oil-soluble tetramer (maleic anhydride-styrene-octadecyl acrylate-acrylamide)viscosity reducer MSAZ was synthetized for the Gudong heavy crude oil in Shengli oilfield with high amount of asphaltene and resin. The ratio of monomers,reaction temperature,reaction time and quantity of initia-tor were studied to find the best synthesis condition. The best synthesis conditions are a temperature of 85 ℃ and a reaction time of 6 h at the monomer ratio of n(octadecyl acrylate)∶n(styrene)∶n(maleic anhydride)∶n (acrylamide)= 4.25 ∶ 3 ∶ 2 ∶ 0.3. At 50 ℃,viscosity reduction rate could reach to 75.8% with 500 μg/g of MSAZ dosage. Surfactants such as lauryl sodium sulfate (SDS),cetyltrimeth-ylammonium bromide (CTAB),polyethylene nonyl phenyl ether (NP-7 ),were mixed with MSAZ, respectively to improve viscosity reducing ability. At the test temperature of 50 ℃,viscosity reduction rate reaches to 85.2% using 500 μg/g of MSAZ mixed with 0.7% of SDS. Surfactants with acidic functional groups in ends show a higher viscosity reduction rates than those with basic functional groups in ends. Molecular weight and distribution of MSAZ analyzed by GPC are that Mw is 20—30 thousands, Mn is 10—20 thousands and polydispersity index is about 2. The experimental results show that within the polymer intrinsic viscosityη of around 11—12 mL/g,MSAZ gives the best viscosity reduction re-sults.%针对胜利孤东稠油胶质、沥青质含量高、黏度大的特点，制备了一种马来酸酐-苯乙烯-丙烯酸十八酯-丙烯酰胺的四元聚合物 MSAZ 油溶性降黏剂。考察了单体配比、反应温度、反应时间、引发剂用量等制备条件对 MSAZ 降黏性能的影响，得到最佳的单体配比和制备条件为n（丙烯酸十八酯）∶n（苯乙烯）∶n（马来酸酐）∶n（丙烯酰胺）＝4．25∶3∶2∶0．3、反应温度85℃、反应时间6 h、引发剂用量1．4％。在测试温度50℃，MSAZ用量500μg/g 时，降黏率最高可达75．8％。0．7％十二烷基硫酸钠（SDS）与500μg/g MSAZ 复配时降黏效果较好，在50℃下，降黏率最大可达85．2％。MSAZ 与具有强酸性头部官能团的表面活性剂复配时的降黏效果要优于与具有碱性头部官能团的表面活性剂复配时。使用 GPC 凝胶色谱法表征了 MSAZ 相对分子质量的大小及分布，重均相对分子质量 Mw 为20000～30000，数均相对分子质量 Mn 为10000～20000，多分散性系数 Mw/Mn 为2左右。特性黏数η为11～12 mL/g 时，降黏效果最好。
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