Owing to the importance of excited state dynamical relaxation,the excited state intramolecular proton transfer (ESIPT) mechanism for a novel compound containing dual hydrogen bond (abbreviated as "l-enol") is studied in this work.Using density functional theory (DFT) and time-dependent density functional theory (TDDFT) method,the experimental electronic spectra can be reproduced for 1-enol compound.We first verify the formation of dual intramolecular hydrogen bonds,and then confirm that the dual hydrogen bond should be strengthened in the first excited state.The photo-excitation process is analyzed by using frontier molecular orbital (HOMO and LUMO) for 1-enol compound.The obvious intramolecular charge transfer (ICT) provides the driving force to effectively facilitate the ESIPT process in the S1 state.Exploration of the constructed S0-state and S1-state potential energy surface (PES) reveals that only the excited state intramolecular single proton transfer occurs for 1-enol system,which makes up for the deficiencies in previous experiment.