To study the shear performance of concrete columns corroded by saline soil， apply different preloads to 11 polypropylene fiber lithium slag concrete columns and saline soil environmental erosion tests were carried out at the ages of 0 days， 90 days and 180 days. Then the specimens after erosion were subjected to low cycle level repeated loading tests. The influence of erosion time， axial pressure ratio， and preloads on the shear resistance of fiber lithium slag concrete columns and their failure mechanism were analyzed. The results show that the addition of polypropylene fiber and lithium slag can improve the shear resistance of concrete in saline soil environment； at the same axial compression ratio， with the increase of erosion time， the shear capacity of fiber-reinforced concrete columns shows a trend of first increasing and then decreasing； with the increase of the preloads， the shear capacity of the column increases first and then decreases. When the erosion time is fixed， the shear capacity of eroded members increases after setting the axial compression ratio from 0.2 to 0.3. According to the experimental results， and considering the influence of the fiber on the shear bearing capacity， a formula for calculating the shear bearing capacity of fiber columns is established based on the truss arch model， the fiber effect is considered as a tension field and is analyzed together with the stirrup. The average value of the ratio between the theoretical calculation value and the test value is 0.970， the standard deviation is 0.086， and the coefficient of variation is 0.090. Both two are better matched.