Abstract: This paper presents a little boron permeated on the surface of natural diamond to form boron skin with the ion implantation method. Tests are done to find whether its heat resistance might be improved. A low-energy ion-implantation device has been designed and improved. Two sources (B2O3 and pure boron) have been implanted to the natural diamond with four energies (8.0, 6.5, 4.5 and 2.5 keV). Boron-skin forms on the surface of diamond. The surface of diamond remains to be colorless and transparent after implantation. On the surface of the natural diamond the B1s peak can't be found by XPS test. It is assumed that no boron atoms exist on the diamond surface. But after ion implanting, obvious B1s peak is found on the surface of natural diamond, then its surface structure is analyzed with the surface testing. Tests show that boron atoms and carbon atoms on diamond surface form a boron-carbon structure. After TGA tests, the heat resistance has been improved in almost the same degree when four kinds of energy are used. But it is better when pure B is used than B2O3. It also shows that heat resistance of boron-skin diamond is only dependent upon the B atoms on the surface and is not upon the B atoms below the surface.