Abstract: The detection efficiency of ϕ75 mm×25 mm of ²⁴¹Am standard samples were studied by using laboratory HPGe detection. When we used detectors with the same type of structure to measure a given volume source, the linearity function between the virtual point source and the virtual point detector was established by using LabSOCS software and Monte Carlo method. For a detector, the position of virtual point detector can be fixed by a point source placed at different height, and then, the position of virtual point source can be fixed by using their linearity function. The real calibration process will be carried out by placing a point source at its virtual position, namely, the volume source is replaced with the point source. In conclusion, the position of virtual point source can be obtained through the virtual point detector. This is a completely new technology method, which will be widely applied in radioactive measurement.