ST25 is a key acupoint used in the treatment of ulcerative colitis by moxibustion stimulation, but the biophysical mechanism underlying its effects is still unknown. The aim of the present study was to explore the biophysical properties of ST25 acupoint stimulated by moxibustion in a rat model of ulcerative colitis. The infrared radiation intensity of fourteen wavelengths of ST25 showed significant differences between the normal and model control groups. The intensity of infrared radiation of forty wavelengths showed significant differences compared with the corresponding control points in normal rats. The intensity of infrared radiation of twenty-eight wavelengths showed significant differences compared with the corresponding control points in model rats. The intensity of infrared radiation of nine wavelengths in the herb-partition moxibustion group, eighteen wavelengths in the ginger-partition moxibustion group, seventeen wavelengths in the garlic-partition moxibustion group, and fourteen wavelengths in the warming moxibustion group of the left ST25 showed significant differences compared with that of the model control group. For the right-hand-side ST25, these values were 33, 33, 2, and 8 wavelengths, respectively. This indicated that one possible biophysical mechanism of moxibustion on ST25 in ulcerative colitis model rats might involve changes in the intensity of infrared radiation of ST25 at different wavelengths.