The evolution of the mechanical properties and volumetric deformation of calcium sulfoaluminate cement-based materials with different contents of ramie fiber（RF） was studied through the flexural strength， compressive strength， interfacial flexural-tensile strength， volumetric deformation and infrared spectroscopy analysis. The results show that the flexural strength and compressive strength of calcium sulfoaluminate cement pastes increase first and then decrease with the increase of RF contents（volume fraction， same as follow）， and reaches their peak values when the fiber content is 0.50%. Under constraint conditions， the addition of RF greatly improves the interfacial flexural tensile-strength of cement paste. At 28 days， the interfacial flexural-tensile strength with a fiber content of 0.75% is increased by 31.82% compared to the unconstrained specimen. The expansion of cement paste is increased by RF addition， and its autogenous deformation and drying deformation both grow with the increase of RF. The modified RF can play a stable role in the alkaline condition of cement-based materials， and improve the overall strength of the sample.