In this paper, we investigate the 3PA induced fluorescence emission and the structure/property relationship of two fluorine-based molecules with symmetric D-π-D conjugated structure, which are named as 4-(2-(7-(4-aminostyryryl)-9,9-bis(2-ethylhexyl)-9H-fluorene-2-yl)vinyl) benzenamino (A) and 2,7-bis(4-methoxystyryl)-9,9-bis(2-ethylhexyl)-9H-fluorene (B), respectively. D and π represent an electron-donor and a conjugated π-electron bridge, respectively. Also, we investigate the 3PA charge transfer process of the two compounds with quantum chemistry calculations. An effort has been made to gain insight into the effect of donor groups on the 3PA-induced upconversion fluorescence properties of fluorine-based molecules.