This paper explores the application of supercritical carbon dioxide fluids on the field emission enhancement for vertically aligned carbon nanotubes. The typical heating process cannot effectively activate the deionized-water-rinsed carbon nanotube emitters, exhibiting poorer field emission performance, due to residual moisture uptake in the carbon nanotubes. In contrast, the field emission enhancement can be achieved significantly by applying the supercritical carbon dioxide fluids associated with 3 to 9 vol % propyl alcohol. It is found the cosolvent propyl alcohol plays a critical role in the activation efficiency of supercritical carbon dioxide fluids. A physical model is also deduced to clarify the observation.