A mild synthetic method to prepare dihydroquinolines has been presented. These dihydroquinolines, for the first time, showed great potential for fluorescence detection of the important biorelevant hydroxyl radicals (•OH). Sensitive and selective •OH detection and intracellular organelle-targeted fluorescence imaging of •OH have been demonstrated by using one of the synthetic dihydroquinolines. Moreover, dihydroquinoline has also exhibited promising potential to construct advanced fluorescence probes for •OH with tunable photophysical properties.