A series of novel coumarin derivativescontaining 4,5-dihydropyrazole moiety as potential telomerase inhibitors were synthesized. The bioassay tests show that compound 3d exhibited potentially high activity against human gastric cancer cell SGC-7901 with IC50 value of 2.69 ± 0.60 μg/mL. All title compounds were assayed for telomerase inhibition by a modified TRAP assay, the results show that compounds