Abstract: The evolution law of geometrical dimensions and relative density for P/M FGH95 superalloy during hot isostatic pressing was revealed by the plastisity theory for porous and solid materials. The criterion for uniform compaction of P/M superalloys in cylindrical can was developed. It can be taken as the guide to determine the dimensions of cylindrical can. Applying this method to hot isostatic pressing of FGH95 alloy, the analytical results coincide with experimental data.