The poor cold flow property is one of the main obstacle factors in affecting the utilization of high-proportional biodiesel blends in engines. In this study, methcyclohexyl methacrylate-methacrylate copolymers (MCHMA-R1MC, R1 = C12, C14, C16, C18) were synthesized at various molar ratios by radical polymerization and characterized by FTIR, GPC, and 1H NMR. Their structures and properties areanalyzed and characterized by FTIR, GPC, and 1H NMR. The resulting copolymers were tested as the cold flow improver in terms of cold filter plugging point (CFPP) and solid point (SP) measurement for treated and untreated B20 biodiesel blends (20 vol.% biodiesel + 80 vol.% diesel). Results showed that the CFPP and SP of B20 decreased to a varied extent after MCHMA-R1MC treatment. When the monomer ratio of is 1:7, MCHMA-C14MC (1:7) proved the greatest depression in CFPP and SP of B20 by 18 and 25℃ at 2000 ppm dosage. The effects of MCHMA-R1MC copolymers on crystal behavior was studied through polarizing optical microscope(POM), differential scanning calorimetry(DSC) and viscosity-temperature curves. The results indicated that MCHMA-C14MC could effectively delay the aggregation of wax crystals and change their crystalline behavior by changing the shape of the crystals and inhibiting the formation of large wax crystals, and then lower the low-temperature viscosity of biodiesel blends and make it exhibiting better cold flow properties.