Abstract: Global water conservation assessment could quantify ecological environment protection and high-quality development in various countries and regions. Biophysical quantity and monetary value of ecosystem water conservation services (WCS) in 183 countries were calculated based on the water balance method and alternative cost method. The results demonstrated that: (1) The water conservation services value of the global terrestrial ecosystem was close to 25 trillion USD in 2015, among which China, Australia, USA, Canada and Russia were the top five. The water conservation services value per unit area was 179, 800 USD per km². (2) From 2000 to 2015, the biophysical quantity of water conservation showed a trend of a climb up and then a decrease, with an average annual growth rate of 1.05% and the most significant increase near the Himalayas. The spatiotemporal variation characteristics of water conservation services value were consistent with the trend of ecosystem type transfer. (3) The global developed countries had 9, 900 USD per capita and 236, 000 USD per km², respectively, with good ecological environment endowment. However, some African countries or the least developed countries had a typical lack of ability to transform the value of ecological products, which should increase the value transformation of ecological products. Due to the magnificent population base, China was supposed to enhance the value of ecosystem services and then further enhance the overall per capita level. (4) The cluster analysis results showed that Australia, China, India and Indonesia had the 'highest' level of ecosystem water conservation value, which is in the first echelon as a whole. The results show that the spatial and temporal heterogeneity of global terrestrial ecosystem water conservation services value was significant. Calculating water conservation services value by country and ecosystem type provides an important reference for the global ecosystem services value assessment.