The n-tetradecylacrylate-vinyl acetate copolymer (PPV) was prepared from n-tetradecylacrylate and vinyl acetate. The PPV was employed as pour point depressant to improve the low-temperature fluidity of the -20# diesel from Daqing Petrochemical Company. The result indicated that the solidification (SP) and the cold filter plugging point (CFPP) were affected largely by PPV. And when mass fraction of PPV -14(copolymerization conditions: 80 °C,w（benzoyl peroxide）1％（total weight of raw materials）, n（vinyl acetate）∶n（n- tetradecanolacrylate） = 4∶1 ) in diesel fuel was 0.1%wt, the SP reduced by 15.0 °C, the CFPP reduced by 6.0 °C simultaneously; We analysise the different molecular weight of PPV-14, and discover that the molecular weight of PPV-14 is ralated to the the low-temperature fluidity of the -20# diesel from Daqing Petrochemical Company. When mass fraction of PPV -14(molecular weight is 15000, distribution coefficient is 3.11) in diesel fuel was 0.1% wt, the SP reduced by 18.0 °C, the CFPP reduced by 7.0 °C, simultaneously.