Research on the swelling of gypsiferous rock has practical significance on the stability of tunnel invert arch.The WG consolidation apparatus and TWJ data sampling system were employed for tests，including the free swelling tests with lateral restraint of dehydrated gypsum，anhydrite and gypsum and the swelling pressure tests of dehydrated gypsum and anhydrite.The results indicate that the swelling strain-time curves of dehydrated gypsum and anhydrite behave as “S” curve.The minimum swelling strain of dehydrated gypsum and anhydrite is 9% and 0.4% at 600 min，respectively，while the maximum strain of gypsum is only 0.12% in 40 days，which indicates that the swelling deformation of gypsum is non-significant.The swelling strains of dehydrated gypsum and anhydrite increase with the increase of swelling stresses，and their swelling stress-strains behave as concave shape curve.Based on the test results，the “S” curve model of swelling strain-time was established，which showed a better fitting result than the exponential model.The swelling stress-strain model was also established.Combing with the characteristic-line theory，the characteristic line for anhydrite rock mass was established，which can give guidance to the design of invert arch.