With the single crystals of diamond without boron as starting materials and then by adding boron atoms to their surface aggregate crystals of diamond have been synthesized under high pressure. By the analytical methods of mokifie particle-tracking autoradiography and use of an ion microprobe, the microstructure of the boron-atom distribution in thaggregate crystal of diamond has been directly observed to test and verify the distrbution model of boron atoms. The reasor why the oxidation resistance and the chemical inertia for the aggrgate crystals of diamond containing boron are excellent ar explained.