To　study　the　relationship　between　the　[2　+　2]　photocycloaddition　reactivities　of　1,4-cyclohexadiene　derivatives　(1,4-CHDs)　and　their　structures,　photophysical　properties　of　a　series　of　1,4-CHDs　were　studied　experimentally　and　by　performing　theoretical　calculations.　Specifically,　UV-vis　absorption　spectra　of　these　compounds　in　diluted　solutions　were　acquired　and　the　theoretical　calculations　were　performed　at　the　density　functional　theory　(DFT)　level.　Their　UV-vis　absorption　maxima　were　found　to　be　related　to　the　substituents　on　the　1,4-cyclohexadiene　ring.　To　describe　the　[2　+　2]　photocycloaddition　reactivities　of　the　1,4-CHDs,　time-dependent　density　functional　theory　(TDDFT)　was　used　to　optimize　their　ground-　and　excited-state　structures,　and　their　electronic　excitation　energies　were　calculated　at　the　M062X/def-TZVP　level.　Frontier　molecular　orbitals　and　electron-hole　distribution　analyses　were　used　to　illustrate　the　electron　transition　modes　of　the　1,4-CHDs.　The　differences　between　the　ground-　and　excited-state　structures　of　the　different　1,4-CHDs　were　characterized　by　carrying　out　a　root-mean-square-deviation　(RMSD)　analysis.　The　results　showed　that　the　photophysical　properties　of　1,4-CHDs　are　meaningful　for　explaining　their　[2　+　2]　photocycloaddition　reactivities.