For THUNDER actuator’s special structure, a mixed piezothermoelastic finite element model including 4 displacement nodes, 8 temperature nodes and 2 potential nodes is presented. A general piezothermoelastic finite element equations for THUNDER actuators are deduced by use of the principle of virtual work. From manufacture to application, the thermal deformation in cooling process, the deformation due to repolarization in repoling process and the piezothermoelastic coupling effect in actuating process are studied respectively, and their dynamic analysis are organically linked together through the variable of initial strain. Numerical results show: the mixed finite element model has good precision; it is the relationship of concave curve between the actuating displacement and loads that makes a THUNDER actuator having a good combination property on driving displacement and bearing loads; when temperature is varied in engineering application, thermal strains have a great effect and the pyroelectric effect has relatively small but still noticeable effect on dome height, which reflects the piezothermoelastic dynamic analysis is necessary for a THUNDER actuator to be used more effectively and accurately in engineering application.