We report here a simple approach to reactivation of iron catalysts for improving the efficiency of catalyst-directed surface growth of SWNTs by heating treatment (normally at 450 degreesC for 30 min in air). The heat treatment approach can burn off the amorphous carbon coated on catalysts and may change the interaction between the catalysts and substrate, thus reactivating the catalyst for the further growth of SWNTs. It is revealed that the growth efficiency can be greatly enhanced by this multitime growth and that, finally, a much higher growth efficiency of SWNTs may be attained. Furthermore, by using the SWNTs grown on silica surfaces at the first time as a reference, we looked at subsequent growth after heat treatment and obtained the direct experiment evidence of base-growth mode. This approach will provide a useful way to directly control and monitor SWNT growth.