Three kinds of subgrade soils with different plasticity index are selected from seasonally frozen soil region. Frost heaving ratio of volume and height was performed on the samples exposed to 0 to 8 times closed-system freeze-thaw cycles. The results show that concerning the same kind of soil, the frost heaving ratio increases with the number of freeze-thaw cycles; Frost heaving ratio increases with plasticity index under the same number of freeze-thaw cycles. Multiple nonlinear fitting is adopted for test data. The relationship between frost heaving ratio and plasticity index, freeze-thaw cycles is obtained and shows a good correlation. The relation can provide useful reference for subgrade design and construction in seasonally frozen soil region.