<p>Sulfate in cement and the environment can affect leching of Cr(VI) immobilized in cement paste according to the immobilization mechanism of Cr(VI) in cement paste. In this study, the influence of sulfate in cement and environment on the leaching behavior of Cr(VI) immobilized in cement paste was studied, and the mechanism of the influence of leaching behavior was analyzed by XRD, FTIR and SEM–EDS. Results: The sulfate in cement will affect the adsorption amount of Cr(VI) by C–S–H, which eventually leads to Cr(VI) leaching; The sulfate in the environment will enter the AFt phase, displacing the Cr(VI) that is solidified in the AFt (ettringite, 3CaO·Al₂O₃·3CaSO₄·32H₂O) phase, resulting in an increase in the leaching amount of Cr(VI) that is immobilized in the hydration product in the sulfate environment. When both sulfate ions (SO₄²⁻) and magnesium ions (Mg²⁺) are present in the environment, the sulfate ions and calcium ions (Ca²⁺) will form gypsum, which will reduce the loss of hexavalent chromium (Cr(VI)); The research found that the Cr(VI) that is solidified in cement shows a trend where its leaching amount increases initially and then decreases as the pH value in the environment decreases. The Cr(VI) that is solidified in C–S–H is leached first, while the Cr(VI) that is solidified in AFt is leached later. It is necessary to consider the sulfates in the cement and the environment for the Cr(VI) immobilized in the cement paste.</p>