Water conservation was one of the important ecological service function of terrestrial ecosystems, which covered the hydrological processes of water in vegetation, soil, atmosphere and animal systems. the change in water conservation of ecosystems was not only directly affected the regional ecosystem status (e.g., regional climate hydrology, vegetation and soil conditions), but also restricted the regional social, economic and ecological sustainable development. Therefore, the evaluation of regional ecosystem water conservation function has become an important part of ecological services research. Although there were many achievements in the researches on the conception, calculation of function and value, and transfer of of ecosystem water conservation, and its ecological compensation across regions. There was still no recognized method to evaluate the level of ecosystem water conservation function, therefore, there were no comparison between most of the previous studies on the level of water conservation function. Because the water conservation calculated based on water balance method was mainly restricted by meteorological conditions, the comparability of the level of water conservation function in different periods were also lower, all those factors greatly reduced the application value of the previous evaluation on the level of regional ecosytem water conservation function. In order to solve the problem of poor comparison in the pros and cons evaluation of water conservation, the evaluation method system of grade of water resource conservation function was constructed based on the water conservation benchmark after fitting the dynamic data of China's ecosystem water conservation from 1990 to 2018, and determining the water conservation benchmark of each evaluation unit. Then the pattern and evolution of the grade of water conservation function in the Chinese ecosystems were revealed on the national and regional scales, and its advantages and disadvantages were also illustrated. The main results were as follows:(1) the grade of water conservation of China's national ecosystem was dominated by poor grade, accounting for 44.8% of the total area, and mainly distributed in northwestern China, Qinghai-Tibet Plateau, North China Plain and Northeast China Plain in 2015. The area of the medium grade of water conservation in China's ecosystem decreased significantly from 1990 to 2018, while the area of poor grade of water conservation in China's ecosystem increased significantly, and the areas of the others grades showed no significant regular fluctuations. (2) The grade composition of ecosystem water conservation was different between climate zones because of the differences in climate, ecosystem composition, human disturbance, and so on. Generally, the wetter the climate zone was, the higher proportion of the excellent grades was. There were 10 climate zones which area of the excellent, good, low, or poor grade of water conservation significantly changed from 1990 to 2018. The main performances were that the areas of excellent, good, and medium grades of ecosystem water conservation were significantly reduced, while the areas of poor grade were all increased. (3) Compared with the other two methods, the evaluation method of the ecosystem water conservation based of water conservation benchmark was more comparable and scientific due to the introduction of the research idea of subarea and classification.