Evapotranspiration is a key link of eco-hydrological process. It is very important for the sustainable development of arid and semi-arid areas to master the variation characteristics of evapotranspiration components and its main influencing factors. In this study, perennial (Stipa capillata) and annual (Artemisia. scoparia) plant communities in desert steppe of Ningxia Hui Autonomous Region were taken as the research objects and the small lysimeters were used to monitor the evapotranspiration for three years. The diurnal, monthly, and annual changes of evapotranspiration components were analyzed, and the main environmental factors affecting evapotranspiration components were discussed. The results showed that on sunny days, the evapotranspiration components of perennial and annual plant communities were parabolic, which firstly increased and then decreased. The nighttime evapotranspiration activity is weak, and the accumulated evapotranspiration is low, less than 20% of the total accumulated evapotranspiration for the whole day. There were no significant peaks for each evapotranspiration component during cloudy days, and all daily accumulations were small, with no significant differences in evapotranspiration, evapotranspiration and transpiration between the annual and perennial plant communities. The daily variation of evapotranspiration and evapotranspiration was significantly influenced by rainfall of 10.64 mm/d and above, and the trend of evapotranspiration and evapotranspiration increased with the increase of rainfall, but the transpiration was relatively small. In terms of monthly dynamics, evapotranspiration and evaporation are greater from July to September, accounting for about half of the year. And the evapotranspiration and evapotranspiration are maintained at the lowest level throughout the year in winter and spring. The annual evapotranspiration was closed to the annual rainfall, and the three-year average ratio of plant transpiration to evapotranspiration was less than 10%. In general, the evapotranspiration of perennial plant communities was higher than that of annual plant communities. The Mantel test was used to analyze the main climatic factors affecting evapotranspiration components at different time scales. It was found that solar radiation had a high level of significance with evaporation and transpiration on hourly scale (P<0.01), but a low correlation (r<0.2). On the daily scale, evapotranspiration, evapotranspiration and evapotranspiration had the highest significance (P<0.01) and correlation (r ≥ 0.4) with rainfall. While on the monthly scale, the correlations of rainfall and rainfall rate with evapotranspiration and evapotranspiration were higher (0.2 ≤ r<0.4) but less significant (P ≥ 0.05). Therefore, the influence of evapotranspiration components by environmental factors has a large variation in different time scales, indicating that evapotranspiration components were influenced by a combination of factors.