Nitrate (NO₃⁻) leaching from agricultural soils poses a potential risk for water contamination and a reduction in nutrient use efficiency. However, NO₃⁻ leaching intensity and its driving forces of cultivated Phaeozems, well-known for its high soil organic content and productivity, is still unclear, especially in regions with cool climates. In this study, a process-oriented biogeochemical model named CNMM-DNDC was validated with observed variables including soil moisture, NO₃⁻ concentrations and crop yields, which are closely related to NO₃⁻ leaching. Next, this validated model was used to quantify the NO₃⁻ leaching intensity of Phaeozems cultivated with maize in northeastern China in 1990 − 2015. The regional simulations showed that NO₃⁻ leaching intensities of maize fields (0 − 5 kg N ha⁻¹ yr⁻¹ for most 10 × 10 km² grids) were lower than those in other Phaeozem regions with warmer climates (29 − 49 kg N ha⁻¹ yr⁻¹). In addition, the results of temperature scenarios also imply that global warming could potentially increase the risk of NO₃⁻ leaching from cultivated Phaeozems in this study region with cool climates, due to the high temperature sensitivity. Reducing nitrogen doses would be an effective strategy to alleviate the risk of water contamination by reducing the regional leaching amount by 15 % with 5% less applied nitrogen. The scenario simulation indicates that the incorporation of full straw would lead to less NO₃⁻ leaching in the near term, but more intensive leaching in the long term. A significant nonlinear relationship was found between the simulated NO₃⁻ leaching intensity and the product of average annual nitrogen dose, average annual precipitation and exponential of average annual air temperature at the county scale. This relationship may provide a simple approach for identifying the potential vulnerable zones prone to nitrogen loss by NO₃⁻ leaching. As this study suggests, the process-oriented CNMM-DNDC model shows the capacity to quantify long term NO₃⁻ leaching at the regional scale, which is potentially a robust tool for developing the best management strategies to mitigate/prevent water nitrogen contamination in the Phaeozem regions.