This paper develops an athermalization method to cancel the mismatch of the coefficient of thermal expansion (CTE) that exists in active control mechanisms, through analysis, prototyping, and tests. Essentially, the CTE mismatch between piezoceramics and the other structures made of super invar is cancelled by combing with another metallic part. In addition, this paper clarifies the mechanism of thermal deformation caused by inner structure of a piezoelectric stack actuator. It shows in both finite-element analysis and tests that the CTE mismatch cancellation is affected by the dimension tolerance of the inner structure, but successfully adjustable by the proposed methods. Moreover, the high thermal sensitivity of the actuator is exploited to propose another type of smart actuator, which uses active thermal deformation. This alternative approach is also evaluated through analysis, prototyping, and tests.