Water conservation is an important component of forest ecosystem services, which is involved in the natural processes such as regional climate circulation, hydrologic cycle, vegetation growth and succession, and availability of soil nutrients. Thus it is an important indicator for regional eco-environment condition. Water resources in Three North Shelterbelt Forest Program region are scarce. Many researchers have attributed water scarcity in this area to large-scale artificial afforestation. Other studies have shown that climate change, the industrial development, intensive agricultural irrigation, and overdraft of groundwater were the primary causes of water resource changes. Whatever the reasons are, recent studies have shown that topography, stand condition and quality significantly influenced the regional forest water conservation. It is necessary to dynamically study the forest water conservation and its response to topography, forest condition and quality. This will be conducive to understand the achievements in ecological construction, to promote vegetation construction, and to regulate water conservation services of the Three-north Shelterbelt forest program. This study analyzed literature and applied GIS technology to analyze the hydrological characteristics of different forests, and to develop a method to dynamically assess water conservation services of different forests at a regional scale. We quantified the water conservation services of different forests in the Three North Shelterbelt Forest Program region comparing those services across different types of forests, years and vegetation zones. We also analyzed the respective effects of topography, forest condition and quality on the spatial patterns in forest water conservation services. The results were as follows:(1) the forest water conservation in Three North Shelterbelt Forest Program region has been continually enhanced. It increased from 73.92mm in 1990 to 75.14mm in 2015, and followed a decreasing trend from the east to the west, and from the south to the north. (2) There were significant differences in forest water conservation among different vegetation zones, years, and forests types. Forest vegetation zone was the main body of forest water conservation in the Three North Shelterbelt Forest Program region. The coniferous and broad-leaved mixed forest was the forest type with the highest forest water conservation. (3) The forest water conservation in the Three North Shelterbelt Forest Program region was affected by topography, forest condition, and quality respectively. Except for individual vegetation zone, the forest water conservation in vegetation zone was significantly increased with raised slope degree, vegetation coverage, and vegetation net primary productivity, while was decreased with forest biomass, which was the result of the comprehensive function of regional vegetation adaptation and human disturbance, such as excessive deforestation, destroying trees and reclamation, and vegetation construction and protection. Therefore, the regional forest water conservation can be regulated by adjusting and improving forest structure.