Thiophene and furan at the 9th position of the fluorene were prepared through condensation reaction as the starting materials, followed with formylation on 2th position of thiophene and furan, then the Knoevenagel condensation of intermediate and acrylic acid gave two simple structure dyes F-S and F-O, which were consisted of flourene as the electron donor, while thiophene and furan as the π bridge. All the intermediates and target dyes were characterized by 1H NMR. After testing the optical properties found that only a single atom change lead to a greatly difference about the two dyes. The maximum absorption wavelengths of UV-vis of dye F-O was 22 nm red shift compared to F-S. The batteries were also assembled and tested, the photoelectric conversion efficiency (PCE) of F-O was 2.76 %, while the efficiency of F-S was just 1.98 %. The results illustrated that the introduction of appropriate π bridge structure can significantly improve the photovoltaic properties of fluorene dyes.