We report the dynamic third-order nonlinear optical susceptibilities chi((3)) using the INDO/SDCI method coupled with the SOS method for the different forms of PcTiO films. The calculated values of chi((3)) at a low frequency are found to decrease in the order alpha-PcTiO > Y-PcTiO > beta-PcTiO. and well corresponded to the varied trends in the measurements. A low space symmetrical structure of alpha-PcTiO film has the largest magnitude of which is the contribution from the intermolecular interaction. The electron transfers from macrocycle pi orbitals to metal Ti 3d orbital make a substantial contribution to the third-order NLO response for the PcTiO. (C) 2002 Elsevier Science B.V. All rights reserved.