Plasmonic nanoparticles induced localized heating has drawn much attention due to its current and potential applications like solar energy harvesting and storage, photothermal therapy, nanosurgery, nanochemistry, optofluidics, and surface-enhanced Raman spectroscopy. Ultilizing a nanoparticle or other sorts of nanostructures under the illumination of strong monochromatic light can create a localized nanoscale source of heat with minimum influence on its surrounding area. In the present work, we studied quantitatively the amplification effect of a nanosphere dimer on the hot spot located in the interparticle gap. It is found that in the nanotrimer system under consideration, the thermal amplification efficiency increases with the increasing of the size of amplifier, under the illumination of monochromatic light. However, high localized photothermal conversion efficiency does not necessary mean high local temperature, since the local temperature rise is induced by two independent effects, namely, thermal superposition effect and plasmonic coupling effect. The contribution of these two effects on the temperature rise of the hot spot is also investigated. At last, we discussed the possibility of using the hot spot effect on the heat-assisted magnetic recording system to reduce the size and complexity of the writing head by replacing the gold nanoheater with metal nitrides.