The deep-sea region has great economic potential due to its rich mineral, energy, and biological resources. Dissolved deep-sea minerals are important markers that reflect the activity and evolution of seafloor hydrothermal fluids. Herein, a novel in situ measurement method is proposed to estimate deep-sea sulfur ion concentration. The all-optical fiber transmission mode is adopted as a design concept, with a high-power mini light-emitting diode (LED) used as the excitation light source. The chemical display method, which is based on the Lambert-Beer law, is combined with the full spectrum detection method to measure the concentrations of deep-sea ionic minerals. The self-established adaptive Savitzky-Golay filtering algorithm is employed to achieve a threefold to sevenfold improvement in the spectral signal-to-noise ratio for data processing. The results reveal that the proposed system can achieve a detection sensitivity below 0.1 μmol/L under the conditions of 1 s time resolution and a 20 mm effective optical path. Furthermore, a good linear response characteristic ［relativity (R2)>0.99］ is obtained in the 0-32 μmol/L concentration range.