Three anthracene-dicyanovinylbenzene compounds with different length spacer were designed and synthesized. The mechanism of the intramolecular electron transfer of An-DCVB was investigated with absorption, fluorescence spectra, laser flash photolysis and single photon counting. Upon irradiation, intramolecular electron transfer from moiety An to DCVB occurred, exciplex formed and triplet energy transfer took place. The influences of the length spacer on molecular conformation, exciplex formation and triplet energy transfer were discussed.