Fissure extending in loess is one of the main causes of resulting in the collapse of loess, and unloading of loess cut slope impels fissure extend In order to simulate stress paths of loess under unloading of cut slopes, loess samples were carried on lateral unloading test by triaxial apparatus (GDS).). Combined with CT scanning image analysis, the change law of fissure extend of loess under unloading was disscured. The results show that with the increase of the unloading weight, the sensitivity of the loess was increased. The results show that with the increase of the unloading weight, samples change from elastic deformation to elastic-plastic and plastic deformation. With the increase of The larger the unloading velocity, the elastic-plastic deformation changes from elastic deformation to elastic-plastic and plastic deformation. With the increase of the larger the unloading velocity, the elastic deformation become smaller, the elastic-plastic and plastic deformation become larger, and shear stresses of samples become larger.