The humidity-controlling material is of important significance to the comfort level of housing environment and consume of energy.In this study, rice straw fiber was semi-carbonized before used in the cement building materials.The semi-carbonization means that the rice straw fiber is carbonized at low temperature (about 300 ℃), the cellulose, hemicellulose and lignine, which can delay hydration hardening time seriously, are incomplete decomposed.Thereby admirable humidity-controlling materials were prepared using semi-carbonized plant fiber.The foam gypsum and vermiculite mortar were selected as basis materials, which were added different amount of semi-carbonized rice straw fiber to achieve porous humidity-controlling materials.The strength, density, the capacities of moisture absorption and desorption and SEM images of the two kinds materials for three times were investigated.As a result that, the density of the materials is below 900 kg/m3, compressive strength meet to require of unloaded-bearing wall materials.The maximum 24 h maximal absorbing moisture value of foam gypsum material reached 32.1 kg/m3, the capacity of moisture desorption is accounted for 75.39% of the maximal absorbing moisture value, and the final equilibrium absorption moisture content is 10.5 kg/m3 at 10% amount of semi-carbonized fiber.And the maximum 24 h maximum hygroscopicity of vermiculite mortar material reached 33.4 kg/m3, the first time desorption is accounted for 74.02% of the hygroscopicity, and the final equilibrium moisture absorption content is 11.3 kg/m3.From the SEM images, the graduation is formed between micropores in the semi-carbonized plant fiber and the macropores introduced, the macropores would increase desorption surface area and the micropores adsorb and immobilize water molecules, so the materials have a very good self-adjustment function of moisture.