The infrared thermal imagery technology has received more and more attention in the civil engineering because of its unique advantages. But it is worthily further study in theory and experiment in the aspects of its applicable scope, test method, result and precision analysis and so on. Using finite element simulation method to study infrared non-destructive testing process can remove all kinds of noise and other external condition influences in the actual test.It also helps to study the influence of various thermal parameters on sensitivity testing. Thus it provides the theory basis and the technical reference for the actual infrared non-destructive testing.