Abstract: The strength characteristics of biopolymer (XG)/sand composites were studied by unconfined compres-sive strength test and triaxial shear test. The effects of different XG contents (mass ratio to sand) and different dry-wet cycles on the strength characteristics of XG/sand were analyzed. The microstructure of different XG/sand was analyzed and studied by scanning electron microscope and low field NMR analyzer. The results show that with the increase of biopolymer content, the unconfined compressive strength, peak deviator stress and cohesion of XG/sand increase, and the internal friction angle varies in the range of 27°-32°. With the increase of the number of dry-wet cycles, the unconfined compressive strength, peak partial stress and cohesion of XG/sand decrease. The strength of XG/sand decreases about 29% after 4 dry-wet cycles. With the continuous increase of the number of dry-wet cycles, the decrease of strength is stable at about 20%. Biopolymers can form a large number of network structures on the surface and pores of sand. A large number of network structures are connected to each other as a network membrane, connecting the sand as a whole. The change of water in the environment will cause some damage to the reticular membrane, which reduces the mechanical properties of XG/sand. However, XG/sand still has strong structural and mechanical properties compared with the unmodified sand.