To investigate the dynamic evolution law of salt heave and frost heave of saline soil in the Daqing area during freeze-thaw cycles and its influence on the structural safety of canal slope lining, NaHCO₃ silty clay was selected as the research object. A scaled model test of canal slope was conducted. The Cambridge model was modified by introducing the salt heave effect. A water-heat-salt-stress four-field coupled finite element model of a trapezoidal canal slope under open conditions was established. The accuracy of the model was verified. The test results show that under unsaturated conditions, when the NaHCO₃ concentration in soil is 0.93% and 3.16%, respectively, the salt-frost heave force exhibits peak characteristics with a minimum value and a maximum value. Under freeze-thaw cycles, the maximum principal tensile stress of the slope foundation soil reaches 1.4 MPa. This value exceeds the design tensile strength of C20 concrete. This result indicates that the existing lining structure has a risk of cracking. With the increase in freeze-thaw cycles, the freezing front gradually extends inward. After the fourth freeze-thaw cycle, the maximum disturbance depth of the slope surface reaches 1.75 m. At the same time, soil moisture migrates upward significantly. The water content at 0.5 m above the canal bottom increases by about 2%. Salt accumulates significantly at 3 mm below the slope surface. The salt supply layer is mainly distributed within the depth range of 0.1 m and 0.25 m. Based on the experimental and numerical results, it is suggested that a large-diameter rockfill layer should be installed during the excavation stage in canal slope engineering in the Daqing area. C25 concrete should be used as the slope lining material. These measures improve the overall stability and durability of canal slopes under salt-freeze conditions.