Abstract: To reveal the effects of preloading and seawater erosion on the strength of solidified soil, the erosion simulations of soda residue (SR)-ground granulated blast furnace slag (GGBS)-carbide slag (CS) solidified soil subjected to different preloading levels are conducted. The unconfined compressive strength and X-ray diffraction tests are carried out, and the influences of the preloading level and erosion age are mainly discussed. The results show that with the increase of the preloading level, the strength of solidified soil increases first and then decreases. The strength of the solidified soil reaches its maximum at the preloading level of 40 % or 60%, but decreases under seawater erosion at the preloading level of 80%. When the preloading level is 60% and eroded by seawater for 120 days, the strength values of the SR-GGBS-CS solidified soil and cement solidified soil are 60 % and 84 % of the strength before erosion, respectively. High preloading and long-term seawater erosion generate large quantities of the secondary ettringite and hydrated calcium chloroaluminate, whose coupling effects lead to significant deterioration of the solidified soil.