A novel compound 1,3-diphenyl-4-(4���-fluoro)benzal-5-pyrazolone N(4)-phenyl semicarbazone (DP4FBP-PSC) has been synthesized. X-ray single crystal structure analysis shows that the compound has interlaced structure linked by intermolecular hydrogen bonds. The results of fluorescence emission spectroscopy, UV-Vis reflection spectroscopy and the reaction rate constant indicate that DP4FBP-PSC is photochromic material. Its photochromic mechanism was investigated by structure analysis. �� 2005 Elsevier B.V. All rights reserved.