Using the 2-year observations from moored array from the Kuroshio Extension System Study (KESS), the process of downward energy transfer was investigated. The SVD analysis indicates that the correlation coefficient between upper- and bottom-ocean kinetic energy reaches 0.87, accounting for 47% of the total variances, demonstrating that fluctuation in the upper-ocean jet has a substantial effect on deep-ocean flows. During three large meander occurrences, the sea surface height (SSH), the vertical movement of the thermocline, the deep pressure anomaly, and the abyssal flow exhibit coherent variation. Upper ocean meanders transfer energy to deep ocean low-frequency motions (periods > 3 days), accelerating the deep ocean currents to 0.26, 0.20, and 0.28 m/s, which are several to ten times their background velocities. The upper-to-deep energy transfer rate was calculated as ~6%. The additional deep ocean low-frequency kinetic energy (LFKE) cascades energy into motions in the inertial kinetic energy (NIKE, 0.8~1.2f) or high frequency kinetic energy (HFKE, > 1.2f ) bands, resulting in ten times kinetic energy augmentation at their bands. Near inertial waves (NIWs) appear to catalyze nonlinear wave‐wave interactions, which further cascade energy from NIWs and internal tides to higher‐frequency internal waves above fk1 frequency. A physical model is presented for understanding the downward energy transfer mechanism. We argue that the downward transfer of energy from the upper ocean to the deep ocean may play a significant role in generating turbulent mixing in the deep ocean.