Abstract: To reveal the dynamic deformation characteristics and pore structure evolution mechanism of steel slag synergistically modified cement soil with calcium carbide slag (SCMCS) under wet-dry cycles and cyclic loading, dynamic triaxial tests and mercury intrusion porosimetry tests were conducted. Under cement content of 7% and a total steel slag and calcium carbide slag content of 20%, five SCMCS mix proportions were designed to explore the effects of solid-waste proportions on cumulative plastic axial strain, shakedown behavior, and pore structure. The dynamic triaxial test results show that under standard curing conditions, the cumulative plastic axial strain of SCMCS reaches 0.19% when the mass ratio of steel slag to calcium carbide slag is 9∶11 (SCMCS-4). Wet-dry cycles increase the cumulative plastic axial strain. After seven wet-dry cycles, SCMCS-1 shows the largest increase, whereas SCMCS-4 shows the smallest increase. Wet-dry cycles promote the evolution of the cumulative plastic axial strain rate from the plastic creep stage to the incremental collapse stage, while SCMCS-4 maintains a relatively low strain rate and exhibits better delayed failure resistance. Mercury intrusion porosimetry results show that, with increasing wet-dry cycles, micropore and small-pore proportions decrease, whereas mesopore and macropore proportions increase. The most significant pore structure degradation occurs after the third wet-dry cycle. SCMCS-4 maintains high micropore and small-pore proportions and inhibits macropore development, showing the best pore structure stability. Finally, wet-dry cycle number was introduced into the cumulative plastic axial strain model, and a prediction model considering wet-dry cycles and cyclic loading was established. Good agreement has been found between fitting results and measured data. The research findings reveal the anti-desiccation degradation mechanism of SCMCS from both dynamic deformation response and pore structure evolution, providing a reference for road engineering construction and industrial solid-waste utilization in coastal areas.