Thermodynamic analysis was performed with respect to the effect of surface tension on the expansion characteristics of a one-dimensional nanoscale liquid Ga column inside a carbon nanotube. The analysis showed that the surface tension affects the column inner pressure, and that the smaller the column diameter, the greater the surface effect. Based on the analysis, it is quantitatively explained why a liquid Ga column with 75 nm diameter has virtually the same expansion coefficient as that of Ga in a macroscopic state in the range of 50 to 500℃, and suggested that the volumetric expansion coefficient can be directly used for the calibration of a given nanothermometer with a diameter larger than 10nm.