The Study of simulated experiment on decay of γ ray in petroleum pipeline of different thickness of pipeline wall is carried out with γ ray transmission method. Experimental Provision consists of 137Cs γ radiators and NaI (TL) scintillation detector. To substitute iron plate of different thickness with thermal insulating layer for petroleum pipeline of different thickness of pipeline wall

we have measured response curve of iron plate with thermal insulating layer

and compared with the result of theoretical account.