Abstract: Objective To investigate the effects of ultraviolet A （UVA）, narrow-band ultraviolet B （NB-UVB） and three immunosuppressants on CXCL9/Mig secretion by a human keratinocyte cell line, HaCaT. Methods Enzyme-linked immunosorbent assay （ELISA） was carried out to detect the levels of CXCL9/Mig in the culture supernatant of HaCaT cells, which had been cultured for 24 hours after being exposed to various doses or concentrations of UVA, NB-UVB, dexamethasone, methotrexate and triptolide. Results The CXCL9/Mig secretion by HaCaT cells was significantly inhibited by UVA （2, 4, 6, 8 J/cm2）, NB-UVB （0.1 J/cm2）, dexamethasone （0.001, 0.01, 0.1, 1, 10 ng/mL）, triptolide （0.01, 0.1, 1 ng/mL） and methotrexate （1, 10 ng/mL）, respectively （P < 0.05）. Conclusion The therapeutic mechanisms of UVA, NB-UVB, dexamethasone, methotrexate and triptolide for Th1-dominated skin diseases may be associated with their inhibitory effects on CXCL9/Mig secretion by keratinocytes.