The mechanical properties of two types of specimens were tested,which were sampled from different direction (transverse and longitudinal) in two PBX formed by mould pressing and isostatic pressing respectively. The experimental results show that both of tensile and compressive strength between transverse and longitudinal directions in isostatic pressing PBX are almost the same,in other words,isostatic pressing PBX is mechanically isotropic; and although compressive strength between transverse and longitudinal does not show obvious difference for mould pressing PBX,but tensile strength shows apparent difference,mould pressing PBX is anisotropic.