Abstract: Using the daily meteorological data from 50 meteorological stations in Liaoning province from 1961 to 2015,the amount of reference crop evapotranspiration (ET₀) was calculated using the Penman-Monteith formulation,and its variation trend and mutation characteristics were analyzed statistically using MK (Mann-Kendall) test and R/S (Re-scaled Range) methods.The results show that in the recent 55 years,the average value of the amount of ET₀ in the whole year and each season presents a downward trend,with a maximum declining rate appearing during the 1960s to 1970s,and from east to west,it gradually increases.The average values of wind speed and sunshine hours are the main meteorological factors to influence the amount of ET₀.There is a Hurst phenomenon in ET₀ and meteorological factors.It suggests that the variation trend in the future will be similar to the past one,i.e.,the decreasing in wind speed and sunshine hours will result in the continuously declining in ET₀ in the future.