Abstract: A series of CU triaxial tests on clay reinforced by basalt fiber are performed under controlled soil dry density conditions, and the ratio of basalt fiber content to dry soil by weight is 0.0%, 0.1%, 0.2%, 0.3% and 0.4%. The test results show that: (1) The failure of specimens are all tympanous and plastic obviously. (2) The effective cohesion of the reinforced clay soil increases obviously, but the effective internal friction angle only changes a little. The effective cohesion is the maximum under the fiber content of 0.3%. (3) The stress-strain relationships of the basalt fiber-reinforced clay soil possess weak hardening characteristics generally, and they can be fitted by hyperbolic curve. The parameter b of the fitting results decreases with the increase of confining pressure under the same fiber content, and the variation of b with the fiber content is related to the magnitude of confining pressure under the same confining pressure.