The photothermal conversion and thermal preservation effect on wool fabric treated with vanadyl (2+) sulfate (VOSO4) and dyed were studied. It was found that the temperature of wool fabrics dyed with gallic acid, or reddish, greenish or bluish acid dyestuff after treated with VOSO4 increases to over ≈15 ºC higher than that of untreated wool and black-dyed wool without VOSO4 treatment, when they are irradiated with light for 10 min. The VOSO4-treated wool also shows higher thermal preservation after turning off the light. Visible light with longer wavelength and infrared light contribute chiefly to the photothermal conversion effect. The photothermal conversion effect of the treated and dyed wool is independent of the colour of wool samples. It can be said that the photothermal conversion effect is due to the function of vanadium adsorbed on the fibre. Wool, silk and nylon fabrics are dyed with the combination of VOSO4 and Cyanine 5R. Wool, silk, nylon, cotton, rayon and acetate fabrics treated with the combination show the photothermal conversion effect. The treated wool fabric exhibits the highest photothermal conversion (highest temperature) among them.