Coumarin derivatives were shown to possess valuable pharmacological properties such as anticancer/anti carcinogenic, anti-inflammatory, anti helicobacter, anti genotoxic, neuroprotective and dietary effect. In this study, novel coumarin derivatives structurally related to 7-geranyloxycoumarin were effectively synthesised in good yields by Cs2CO3/acetonitrile in mild condition. The synthesis of geranyloxycoumarin derivatives in weak base(Na2CO3, K2CO3, Cs2CO3 etc)/CH3CN at room temperature obtained in good yield. On the other hand, the reaction of geranyloxycoumarin formation in strong base(NaOH, KOH, CsOH etc)/CH3CN at reflux condition obtained in low yield.