A thermal sensitive material, i.e. its mechanical properties strongly dependent on temperature, is periodically embedded in a series of metallic films acting as heat sources. The periodical thermal field transforms the homogenous structure into a functionally graded phononic crystal. Band gaps can be hence manipulated by the applied periodical thermal field. A transfer matrix method incorporated with a laminated model is employed to solve the band gaps of SH-wave. Numerical results show that periodic thermal field can manipulate the band widths, locations and numbers of band gaps significantly.