Abstract: Selecting thermal stimulating signal is pivotal problems in thermal wave testing. In order to resolve it, beginning with the theory of thermal wave testing, a partial differential equation that could work out temperature distributing of sample was established. By analyzing equation group, the relationship between intensity of thermal stimulation signal and temperature change in direct proportion, which was proved by numerical through ANSYS. This conclusion indicates that, when boosting up intensity of thermal stimulation signal, the biggest temperature change will increase in proportion as in pulsed thermography, temperature change will increase in proportion as in step heating thermography; breadth change will also increase in proportion as in lock-in thermographic testing, which provides theoretical basis and implementing measure.