Abstract: In order to predict responses of ET0 to perturbation of climate variables, growing seasonal ET0 for 34 meteorological stations in West Songnen Plain from1951 to 2001 was estimated with the FAO-56 Penman-Monteith equation. Sensitivity coefficients of ET0 to air temperature, wind speed, sunshine hours and relative humidity were calculated and their tempo-spatial characteristics were analyzed. The results show that relative humidity is the most sensitive variable to ET0 in general for study area, followed by air temperature, wind speed and sunshine hours. From May to September, the highest sensitivity coefficients to air temperature and sunshine hours is in July, while the lowest sensitivity coefficients to wind speed in July. The absolute sensitivity coefficients to relative humidity increases from May to September. The absolute sensitivity coefficients to all climate variables indicate large spatial variability. The high value area of sensitivity coefficients to air temperature, sunshine hours and wind speed is in the southwest study area, while the low value area of sensitivity coefficients to relative humidity is in the southwest study area with the high value area in the northeast study area.