For grasping the impact of reinforced fiber on swell-shrinking property and other mechanics performances of expansive soil, a great deal of indoor experiments are conducted to study various relationships among fiber content and other mechanics performances, i.e. swell-shrinking property, compressibility, stress-strain, and shearing strength. The study results show as follows: The swell-shrinking property apparently decreases with the increase of fiber content; the limiting strain will increase with the increase of fiber content, but the stressdrop will greatly decrease as the damageof the soil; fiber expansion soil’s ?cohesion will increase but internal friction angle will decrease as the fiber content increase, but when the content is added to a certain extent, the former will decrease and the latter will increase.