In the in situ γ spectrometer based measurement of " hot particular”, " radioactive collection point” and " radioactive collection area”, only the position of the pollution source can be located roughly, but its boundary parameters such as the thickness of pollution source cannot be given. In this paper, the application of virtual technology to the scanning of γ spectrometer is studied. We convert γ spectrometer measurement objects into a four-layer theoretical model, which are attenuation thickness + radioactive hot area + attenuation thickness + disturb source. Then, the source item layer is virtualized into a point source by using virtual technology. So, the theoretical model is further simplified. Then the detection efficiency and peak/valley ratio parameter of source term are simulated by Monte Carlo method. Finally, the source term parameters are retrieved by using the least square method, and thus establishing the theoretical method and procedure of inversion calculation of source boundary parameters. In this paper, the theoretical and experimental results are shown to be consistent with each other. So, this method is verified to be correct and practicable. Currently, the method can accurately determine the depth distribution parameters of radioactive contamination area for uniformly distributed radio nuclides. In conclusion, the technical achievements can be used to accurately determine the boundary range of the radioactive hot zone, thus realizing the purpose of reducing the waste disposal capacity during the treatment. At the same time, the determination of the inert layer thickness parameters of the target nuclear warhead of Nuclear Test Ban Treaty has a significant reference value.