Abstract: As a rule, the thickness of wall painting plaster in Tibet is less than 10 cm. The ground penetrating radar (GPR) is applied to detection of delamination beneath wall painting plaster, It is quite a challenge task to remove directly the coupled noise waves in the radar profiling. So, size of the delamination can be determined accurately. Replica of Tibetan wall painting plaster is made and regular voids with different depths and sizes are set inside it. Then, the forward modeling detection is carried out in the replica in order to get appropriate parameters for acquisition of radar data, to find effective filters for signal processing, and to compare the performance of different antennas. Specifically to the RAMAC/GPR and its accessory software of Ground Vision, it is suggested that the depth of time window be about 3 ns and sampling frequency not less than 142 GHz, and that band pass filter and background subtraction are the two most useful filters in signal processing. When the antenna and the fine plaster are well coupled, both antennas at nominal center frequency of 1.6 GHz and 2.3 GHz are capable of detecting void located at a depth of about 3 cm and a size of around 2 cm. The vertical resolution limit of 1.6 GHz antenna is near 0.5 cm in size.