In this article, two novel donor polymers containing fluorine atoms at ortho-position of alkxoyphenyl group in benzodithiophene (BDT) units are constructed. Compared with the reference polymer(P1) without fluorine atom, the polymers with fluorine atoms (P2 and P3) show their great different electrochemical properties, optical properties, morphology and hole mobility. Most significant change is their photovoltaic performances. The devices formed by P2 and P3 show much higher power conversion efficiency (PCE), 5.44% and 6.12% ， respectively. The reasons should be that the incorporation of fluorine atom at ortho-position of alkoxyphenyl side chains increases the oxidation potential, decreases the highest occupied molecular orbit (HOMO) level of donor polymers, and thus increases the open circuit voltage (Voc) in device. Moreover, the linear hexyl side chain of P3 causes much higher PCE because it generates better molecular aggregation and hole transport in device.