The quantitative study of the sulfate content in natural fluid inclusions (FIs) will help our understanding of the processes of metal transport and related mineralization. The sulfate-rich FIs typically contain several types of sulfates with diverse cations such as Na⁺, K⁺, and so on. In order to get the sulfates contents in natural FIs, in situ Raman spectral quantitative calibration method is used to calibrate the Li₂SO₄, Na₂SO₄, K₂SO₄ and Cs₂SO₄ solutions at temperatures ranging from 25 °C to 250 °C in our study. The results show that the A(SO₄²⁻)/A(H₂O) ratio increases linearly with increasing mSO₄²⁻ in sulfate solutions containing single cation of Li, Na, K or Cs at the set temperatures, where A is Raman peak area and m is molality (mol/kg H₂O), and a negative linear relationship exists between k (quantitative calibration coefficient) and temperature for sulfate solutions with specific cations up to 250 °C. Meanwhile, the slopes and the intercepts of the k-T correlation curves are obviously different among sulfate solutions with different cations, and the coefficients k of these sulfate solutions at certain temperature decrease with the increase of atomic number of the cation, in accordance with the following order: Li⁺ > Na⁺ > K⁺ > Cs⁺. As Na⁺ and K⁺ are the main cations in the natural sulfate-bearing FIs, the quantification of the multi-cation (Na ± K ± Li) sulfate solutions was evaluated by using the Raman quantitative calibration curves of Li₂SO₄, Na₂SO₄, K₂SO₄ and Cs₂SO₄ separately, the errors exist due to the use of calibration curves with different cations; the average concentration errors derived from the use of Na₂SO₄ or K₂SO₄ Raman quantitative calibration curves are within about 5 %, while those from the use of Li₂SO₄ or Cs₂SO₄ Raman quantitative calibration curves are within about 15 %. Therefore, the acceptable errors suggest that the calibration curves of individual sulfates can be applied to the determination of sulfate content of natural sulfate-bearing FIs.