The present invention provides a method of detecting helicase activity in a test solution, providing a substrate solution containing a double-stranded DNA, wherein said double-stranded DNA is a substrate for a helicase to be detected; (b) introducing the substrate solution to the test solution to form a reaction solution; (c) applying a luminescent probe into the reaction solution to form a mixture; and (d) measuring a luminescent response of the luminescent probe in the mixture, wherein the luminescent response corresponds to the helicase activity in the test solution. The present invention also refers to a method of screening a potent luminescent probe for detecting helicase activity, and a series of luminescent Ir (III) complexes. Said luminescent Ir (III) complex comprises an iridium-containing dimer and a nitrogen-containing ligand