The supply of nutrients from depth into the euphotic zone has been hypothesized as a primary source to sustain the new production in the oligotrophic ocean. The diapycnal fluxes of nutrients are an important nutrient supply mechanism but have not been adequately constrained due to spare observations and the dynamic nature of turbulence. Here we show the diapycnal fluxes of nutrients, including diapycnal diffusive (F_diff) and effective diapycnal fluxes (F_e), in the oligotrophic west North Pacific Subtropical Gyre (wNPSG) based on three cruises covering spring, summer and winter. The diapycnal fluxes of nutrients are notably higher in the south wNPSG close to the North Equatorial Current than those in the central wNPSG. At the base of the euphotic zone, the averaged F_diff (F_e) of NO₃^- + NO₂^- (NOx) is 0.045±0.049 (0.064±0.072) mmol m^-2 d^-1 in spring, and 3 to 6 times larger than 0.011±0.009 (0.012±0.009) and 0.009±0.006 (0.011±0.009) mmol m^-2 d^-1 in summer and winter, respectively. The seasonal differences of F_diff (F_e) are primarily influenced by the seasonal differences of turbulent kinetic energy dissipation rates. Spatially, there are good linear relationships between decimal logarithm of F_diff (F_e) and the decimal logarithm of nutrient gradient, suggesting that spatial variations of F_diff (F_e) are primarily influenced by nutrient gradients. Applying these relationships, we further predict the climatological distributions of F_diff (F_e) using the nutrient data collected from World Ocean Atlas (WOA18) in the NPSG. It suggests that the F_diff (F_e) is 0.027±0.052 (0.034±0.066) mmol m^-2 d^-1, and contributes to 22±44% (28±55%) of the nitrogen required by new production in the NPSG.