Abstract: The visible spectra and fluorescent spectra of safranine T(ST) solutions with the presence of sodium hexametaphosphat(SHMP) were investigated. The results showed that ST tends to aggregate when SHMP was presented and a heteropolymer appeared by electrostatic attraction between ST and SHMP in the HAc-NaAc buffer solution, which results in a new peak appeared in 476 nm in visible absorption spectra and the intensity of the absorbance and the fluorescence decreased. Meanwhile, the fluorescent lifetime of the ST was not changed, which suggested that the fluorescence of ST is statically quenched by SHMP. Based on the change of absorbance, we have established a new method to detect the SHMP. Under optimized conditions, the linear range was 1.0×10^-6~1.1×10^-5 mol/L with the detection limit of 3.4×10^-7 mol/L. The application of the established method in the determination of tea drink samples gave a recovery rate of 95.0%~104.0%, with a relative standard deviation of less than 4.6%.