The thermal stabilities and mechanical properties of explosives are important factors affecting the safety of weapons. In order to improve the thermal stability of hexanitrohexaazaisowurtzitane（CL-20） and1，1-diamino-2，2-dinitroethylene（FOX-7） explosives and the mechanical properties of the CL-20 and FOX-7 based PBXs， modified CL-20 and FOX-7 crystals were prepared based on the oxidative self-polymerization reaction of dopamine （DA）. Scanning electron microscope （SEM）， thermal analysis （TG）， dynamic mechanical analysis （DMA）， static contact angle， laser particle size analyzer， high performance liquid chromatography （HPLC）， BMA impact sensitivity， infrared absorption spectrometer and universal material testing machine were used to test the morphology and structure of modified particles， and also the particle size， coating content， sensitivity， thermal decomposition and the mechanical performance of prepared PBX. Results show that DA forms a good polydopamine（PDA） coating layer on the surface of energetic crystals， and different surface coating morphologies can be obtained by adjusting the polymerization time. At the same time， PDA can also improve the interface properties of explosives crystals， which is beneficial to the uniformity of the binder’s distribution. PDA coating inhibits the crystal transformation and increases the activation energy of CL-20， resulting in improved thermal stabilities. The mechanical properties tests showed that the Brazilian strength and compression strength of CL-20 based PBX had been improved by 34.27% and 10.21%， respectively， and the Brazilian strength and compression strength of FOX-7 based PBX had also been improved by 40.44% and 11.92%， respectively. After coating with PDA， the strain of the samples had all increased. In addition， the creep strains of the two explosives were obviously suppressed， leading to enhance creep resistance.