A novel near-infrared fluorescence dye NAPTAM as a water-soluble biological probe was developed. The results showed that the probe has a highly sensitive "turn-on" response to BSA in deionized water, and the emission range of near-infrared spectroscopy is 500–800 nm. A limit of detection of NAPTAM sensing BSA was 0.027 μM. The free NAPTAM has almost no emission in aqueous solution, but the sharp increase of near-infrared emission is observed due to the aggregation state and self-assembly formed by the electrostatic interaction between the positive charged ammonium group of NAPTAM and the negative charged BSA. The zeta potential values displayed that -2.69 mV of BSA was up to -5 mV of NAPTAM/BSA assembly. The relatively experiments of other chemical species to the probe testified that NAPTAM has good selectivity for BSA.