Abstract: Currently, most fluorescent probes can only detect polarity or viscosity value singly, which is ?not conducive to the multifactorial analysis of disease models. Moreover, the reported fluorescent probes that detect viscosity or polarity generally have small Stokes shifts, which can easily lead to large background interference and fluorescence quenching. To this end, we synthesized a novel near-infrared fluorescent probe, YA-B12, based on a fungal fluorescein with bioluminescent properties, which exhibits a large Stokes shift of 178? nm in H2O and fluorescence emission wavelength of 700 nm in aqueous solution, and is capable of responding to viscosity and polarity at the same time. The fluorescence intensity of the probe increased 7-fold from low viscosity (2.4 cP) to high viscosity (360.9 cP), and the fluorescence emission wavelength of the probe was red-shifted from 606 nm to 698 nm from small-polar n-hexane to large-polar methanol. The probe demonstrated high selectivity, high sensitivity, and excellent immunity to interference for the detection of viscosity and polarity.