Bacteria are living things that composed only one cell. There are various types of bacteria in human`s body that function differently, including digestion, destruction of cells that cause diseases, and production of vitamins. However, some bacteria can cause harm to human`s body resulting infections. So, it is very important to detect bacteria efficiently. Nitroreductase (NTR) is a well-known enzyme that exists in bacteria, NTR is often used as a biomarker for detecting bacteria. We presented resorufin-based probes (1 and 2) as a fluorescent Off-On probe for detection of nitroreductase (NTR) activity. Towards NTR activity, these probes gave a fluorescence turn-on at 586 nm with a visual color change from colorless to pink. The sensing ability, mechanism, and enzyme kinetics of the probes for NTR were thoroughly investigated by using absorption, fluorescence, and ESI-Mass spectroscopic analyses. Enzyme efficiencies of the probes were evaluated as 0.260 and 4.368 μM^-1s^-1, respectively, revealing a high sensitivity to NTR activity compared to other previously reported probes. Particularly, probe 1 exhibited an excellent detection ability for NTR activity with a no background signal and a high selectivity in comparison with probe 2. Thus, we are believing that probe 1 as an efficient fluorescent Off-On probe for NTR activity with a fast response, good selectivity and sensitivity, as well as a high signal to noise. We are now going on more experiments using probe 1 for monitoring the change of NTR activity in a variety of bacteria.