Two types of textile fiber modified clay were prepared with used clothing. Through direct shear tests, California bearing ratio(CBR) tests and specifically designed ring cutting tests, mechanical properties of textile fiber modified clay were studied. The test results show that the horizontal shear strength of cotton fiber modified clay is significantly lower than that of plain clay due to the water absorption of cotton fiber. When the fiber content is 1.0%(by mass), the horizontal shear strength of chemical fiber modified clay witnesses a notable increase.When the fiber content is 0.6%(by mass), the cutting resistance of cotton fiber modified clay reaches the peak point. In contrast, the force of chemical fiber modified clay shows the monotonically increase with the increase of the fiber content. Larger water absorptive swelling will occur in cotton fiber modified clay, compared with that of chemical fiber modified clay. The CBR value of textile fiber modified clay slightly increases with a small amount of fiber added. In order to reduce water absorptive swelling, the additional compaction should be done on textile fiber modified clay. In short, the chemical fiber behaves more suitable for modification of clay than the cotton fiber in terms of mechanical properties.