Various 1-substituted thiophenol isochromans were obtained via 1-carboxyethyl-3-methylimidazolium chloride ([COOH-EtMIm][Cl])-catalyzed dehydrogenation coupling reaction between thiophenols and isochroman. After screening the reaction conditions, the optimal conditions were provided as follows: p-toluenethiol 0.5 mmol, isochroman 1.0 mmol, [COOH-EtMIm][Cl] 0.5 mmol, O2 pressure 0.1 MPa, reaction temperature 120 ℃, and reaction time 12 h. With the standard reaction conditions in hind, the catalyst can be reused for 4 times, the gram-scale synthesis of 1-thiophenol isochroman was accomplished, and 12 1-substituted thiophenol isochromans with yields ranging from 52% to 96% were obtained. In addition, the reaction mechanism was proposed: Anion and cation ions of [COOH-EtMIm][Cl] separately activated thiophenol and isochroman, following to be oxidated by O2 and dehydrogenation to form 1- thiophenol isochroman.