Biopolymers can effectively improve the mechanical properties of soil. In order to evaluate the application prospect of biopolymer-modified sludge in practical engineering, the effects of xanthan gum (XG), sodium alginate (SA), and cationic guar gum (GG) on the compressibility and permeability of high water-content sludge were studied. On the basis of one-dimensional osmotic consolidation test, the effects of different types and dosages of biopolymers on the yield stress, compression index, and coefficient of permeability of soil were investigated. Meanwhile, the microscopic mechanism of the modification of high water-content sludge by biopolymer was analyzed by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests. Results show that the compressibility of modified sludge was reduced because of the formation of clay-polymer network structure. With increasing dosage, the compressibility of modified sludge decreased, while the structural yield stress increased gradually. When the vertical effective stress was greater than the structural yield stress, the C_c value of the modified sludge increased significantly, and it further increased with the increase in dosage. The permeability of the modified sludge was significantly reduced. Among the polymers used in the study, XG had the most significant effect, achieved two orders of magnitude when the dosage was 1.5%.