Abstract: The charge transfer complexes (CTC) of 9-p-substituted benzylidene fluorenes (1= p-H, 2=p-Cl, 3=p-MeO) and the electron acceptors, chloranil(TCPQ) and 7,7,8,8-tetracyanoquinonedimethane(TCNQ), were studied. The new absorption peaks attributed to the formation of CTC were observed in the visible region(λ=494-586 nm) by UV spectroscopy. Based on the Bensi-Hildebrand equation, the stability equilibrium constants for the six CTC were determined. The results show that the stability of the CTC increases with the increasing of the electron-donating ability of p-substituente in the benzene ring of the 9-p-substituted benzylidene fluorenes.