Two “D-π-A” type coumarin photosensitizers were synthesized with 7-diarylamino coumarin as the donor, dithiophene or phenylthiophene as the π-bridge, and cyanoacetic acid as the acceptor. Their structures were confirmed by 1H NMR and HRMS and their UV-vis absorption spectra and fluorescence emission spectra were measured. The geometric structures of these dyes were optimized using density functional theory (DFT) in conjunction with the d-polarized 6-31G(d) basis set. Time-dependent density functional theory (TD-DFT) was further used to calculate the absorption spectra and the emission spectra and the structure-property relationship was analyzed. The results showed that 7-difluorenylamino coumarin photosensitizers exhibited relatively smaller energy gap at the ground state (2.31 eV and 2.49 eV) than 7-diphenylamino coumarin photosensitizers (2.49 eV and 2.62 eV) and their energy gap of the excited state was also reduced by 0.52 eV and 0.42 eV respectively. Compared with photosensitizers with phenylthiophene π-bridge, photosensitizers with dithiophene π-bridge had better molecular planarity and their maximum absorption wavelength was shifted bathochromically by 19 nm and 4 nm respectively and the maximum emission wavelength was shifted bathochromically by 16 nm and 9 nm respectively.