The invention provides a fluorine-containing copolymer. According to the copolymer, by adopting 5,6-difluoro-4,7-bi(5-bromo-4-n-hexyl-2-thienyl)-2,1,3-benzothiadiazole as an acceptor and using different ratios of a donor D1 [5,5'-bis(trimethyltin)-2,2'-bithiophene] to a donor D2 [3,4'-difluoro-5,5'-bis(trimethyltin)-2,2'-bithiophene], the fluorine-containing copolymer with different ratios of thedonor D1 to the donor D2 is formed. The photophysical properties of the fluorine-containing copolymer are improved greatly, the short-circuit current reaches 12.40 mA/cm<2>, and the energy conversionefficiency reaches 5.57%. Through a series of characterization means including ultraviolet absorption, cyclic voltammetry, thermogravimetry and gel permeation chromatography and corresponding simulated calculation, it is found that the fluorine-containing copolymer can be used as a solar cell donor unit, and good UV-visible absorption performance and thermal stability are achieved.