The coumarin derivatives of phenols and ethyl acetoaceate were carried out using SO3H functionalized ionic liquid as the catalysts via Pechmann condensation. The optimum reaction condition: n(phenols):n(ethyl acetoaceate)=1:1, microwave irradiation reaction time 10 minute and reaction temperature 100℃. The high yield can reach 94％ in the presence of x([C3SO3Hmim]HSO4)=20% as catalyst, under solvent-free conditions. This method has the advantages of mild reaction conditions, easy operation, high yields and environmental begin. Moreover, the catalyst could be reused for at least four times.