Abstract: Abstract: In order to reveal the difference of evapotranspiration of paddy fields under water-saving irrigation on different scales, the differences of evapotranspiration between field scale and plot scale of paddy field under water-saving irrigation was analyzed based on the field experiment. In addition, the reasons for the difference between evapotranspiration of paddy fields under water-saving irrigation on different scales were investigated in this paper. The evapotranspiration on field scale and plot scale of paddy fields under water-saving irrigation was measured by eddy covariance system and lysimeter, respectively. The results showed that there were significant (p < 0.05) differences between the evapotranspiration of paddy fields under water-saving irrigation on filed scale and plot scale in the whole and early, middle and late growth stages. The variation trend of evapotranspiration of paddy fields under water-saving irrigation on field scale was similar to that on plot scale. But the difference existed on value of evapotranspiration of paddy fields under water-saving irrigation. The evapotranspiration on field scale of paddy fields under water-saving irrigation in the whole growth stages was 18.7% smaller than that on plot scale. The evapotranspiration on field scale of paddy fields under water-saving irrigation in the early, middle and late growth stages was 15.5%-20.5% smaller than those on plot scale. The significant differences (p < 0.05) were also showed between the evapotranspiration of paddy fields under water-saving irrigation on field scale and plot scale in the different growth stages. High significant differences (p < 0.01) were showed between the evapotranspiration of paddy fields under water-saving irrigation on field scale and plot scale in different times (ten days, five days). The evapotranspiration of paddy fields under water-saving irrigation on field scale in ripening stage increased by 7.9% compared to that on plot scale. The evapotranspiration of paddy fields under water-saving irrigation on field scale in other growth stage decreased by 10.2%-29.5% compared to that on plot scale. As the day time shortened, the decreased amplitude of evapotranspiration on field scale of paddy fields under water-saving irrigation increased compared to that on plot scale. Differences between different time steps of evapotranspiration of paddy fields under water-saving irrigation on different scales was caused by underlying surface, atmospheric turbulence conditions, meteorological factors, soil moisture condition, irrigation process and so on.Underlying surface conditions, atmospheric turbulence, the process of water replenishment, the soil water status and meteorological factors were the main reasons for the differences between evapotranspiration of paddy fields under water-saving irrigation on filed scale and plot scale. Relative air humidity and air temperature can lead to the differences of evapotranspiration of paddy fields under water-saving irrigation on different scales. They were the main factors affecting the difference of evapotranspiration of paddy fields under water-saving irrigation on different scales. The effect of meteorological factors on evapotranspiration of paddy fields under water-saving irrigation was mainly related to soil moisture and marginal effect. The reveal of the evapotranspiration differences of paddy fields under water-saving irrigation on different scales can be used for the transformation of evapotranspiration of paddy field under water-saving irrigation on different scales.