Abstract: The pavement of K1516-K1531 section of pingbai highway in Tianyang county of Guangxi province was destructed very much. At eight locations of different destruction of this section of highway the examples of roadbed earth was taken for experiment. The results show that most parts of the roadbed earth is swelled ground. After finding out the deformation law of different kinds of swelled earth, computer was adopted to exemplify and analyze what caused so serious destruction of the pavement. The conclusion is that the swelled ground in roadbed, affected by the outside climate, produces inhomogeneous repeated expansion and contraction deformation, which resulting in the serious pavement destruction. The stronger the expansion and contraction of swelled ground in roadbed- the more serious the destruction of the corresponding pavement. This research provides the theoretical basis for the pavement transformation of this section of highway.