Reference crop evapotranspiration (ET₀) is a key factor in eco-hydrological processes. The study of ET₀ evolution in arid oasis areas not only helps us to understand the response of hydrological processes of oasis in the context of climate change but also has a guiding significance for the efficient allocation of soil and water resources in oasis and the maintenance of ecosystem stability. In this paper, we took the Yellow River Oasis in Ningxia autonomous region as an example, calculated ET₀ based on meteorological data from 1960 to 2019 and the Penman-Monteith model, and used the Mann-Kendall test, relative sensitivity coefficients, and Morlet wavelet analysis to study the characteristics of ET₀ evolution and its driving mechanism in the oasis over the past 60 years. The results showed that: (1) ET₀ of the Yellow River Oasis in Ningxia presented a single peak pattern within a year. The ET₀ was higher from May to July and its accumulated value accounted for 43.6% of the total annual ET₀. The annual ET₀ from 1960 to 2019 was 1226.38 mm and increased with an amplitude of 1.66 mm/a (P ＜ 0.01). However, the fluctuation characteristics of interannual ET₀ were significant in that the ET₀ had no trend before the mutation year of 1988 while it increased or decreased significantly with a cycle of about every decade after that. (2) The annual ET₀ mainly oscillated with cycles of 20-40 and 50-60 years, while its cycles overlapped complicatedly in multiple time scales. Furthermore, the cycle and magnitude of oscillation in different seasons varied greatly. The oscillation cycles in summer and autumn were close to that of the annual, but the oscillation magnitude was stronger than that in winter and spring. (3) Although there were significant correlations between ET₀ and the six meteorological factors used to calculate ET₀, the sensitivity of ET₀ to different meteorological factors varied. The sensitivity of ET₀ on maximum temperature and relative humidity was higher, and the coefficients were 11.58% and 8.40%. (4) There was a strong coupling between ET₀ and the regional climatic changes of the Yellow River Oasis in Ningxia.air temperature sustained warming, relative humidity sustained decreasing, and their aerodynamic coupling result in vapor pressure deficit increasing were critical to promote the enhancement of ET₀. Meanwhile, the mutation of regional climate from wet to dry and the abnormal fluctuation of average wind speed were the reasons to induce the abrupt change of ET₀.