Abstract: The small-strain shear modulus and degradation mode of soils provide the important fundamental information for analyzing and evaluating the dynamic response of soils to earthquake in geotechnical engineering. The resonant column tests on the undisturbed loess with different water contents and confining pressures are carried out to investigate the effects of the water content and confining pressure on the small-strain shear modulus. The results show that the water content and confining pressure have significant effects on the shear modulus and degradation mode of the undisturbed loess. More specifically, udner the same water content, the shear modulus increases with an increase in the confining pressure, while an increase in the water content leads to a decrease in the shear modulus. The loess with high water content and low confining pressure shows faster shear modulus degradation. According to the test results, the correlation between the fitting parameters A and n in Hardin's equation and the water content is analyzed, based on which a modified Hardin's equation considering the water content is established to predict the maximum shear modulus G_max of the undisturbed loess.