Abstract: Based on elastoplastic damage theory, the cracking evolution of a base course has been studied in the condition coupled thermal and shrinkage deformation effects, using the FEM software ABAQUS. The results indicated that: elastoplastic damage mechanics could simulate the production and evolution of cracking on the base course; the space between each cracking could also fit the data obtained from field performance; the shrinkage deformation accounted for the main reason inducing the base cracking, during the maintaining period. The research conclusion can provide a reasonable choice for the construction thickness and set rational separation for joints. At same time, a new user subroutine named UEXPSN (User subroutine to define incremental thermal strains) has been produced. Using this subroutine, shrinkage deformation can be imported in FE calculation. Based on this subroutine, a new research implement which can simulate shrinkage deformation is provided.