In this paper, AuNRs colloids with SPR_L located at ~810 nm and ~1100 nm were synthesized using an improved seed method. Based on the NIR lasers available, photothermal conversion of AuNRs were systematically studied compared with that of water. Under low power irradiation, the highest temperature is obtained when the SPR_L wavelength of AuNRs is equal to the laser wavelength, and temperature of colloid increases from ~20°C to ~65°C. With increasing laser power (such as 6 W), the AuNRs colloid boils within a few minutes, and nanorods undergo a shape deformation from rod to spherical particle and even fusion, and the SPR_L disappears. For further investigation, the obtained AuNRs were coated with SiO₂ shell to form a core-shell nanostructure (Au@SiO₂). The surface coating can be used not only in keeping the stability of AuNRs for further treatment, but also in increasing plasmonic property and biocompatibility. This work will be useful for designing plasmonic photothermal properties and further applications in nanomedicine.