Abstract: The study of deep-sea circulation is key to deep understanding of global climate change, marine ecosystems, and other related aspects. Due to the lack of observational data, numerical simulation remains the primary research tool at present. This paper conducts a climatological numerical study of the North Pacific focusing on the characteristics of deep-sea circulation using a σ-Z-σ hybrid coordinate MASNUM ocean circulation model. The σ-Z-σ hybrid coordinate system takes advantages of both Z-coordinate and σ-coordinate, which makes flexible local grid refinement possible, being an effective method to improve the accuracy of deep-sea circulation simulations. Three sets of gridded observational data, WOA18, MIMOC, and BOA-Argo, are used to evaluate the simulation results. Evaluation indicates that the simulated deep-sea temperature and salinity fields well match the observations. Although there are some discrepancies in the simulated flow field compared to geostrophic currents derived from observations, features such as deep western boundary currents and anticyclonic circulation structures are more pronounced in the simulations than the observed monthly averages, which is closer to the observed flow field in previous studies. Analysis of deep-sea circulation characteristics based on numerical simulations show that there is no significant seasonal variation in the mean values of deep-sea temperature and salinity. However, there is a noticeable seasonal variation in the anomalies of temperature and salinity mean values, especially the significant increase in temperature anomalies during the spring and summer seasons. The horizontal and meridional stream functions exhibit little seasonal variation.