A new passive subsurface radar technique using interference patterns in the spectrum of the Jovian hectometric and decametric radiation (HOM/DAM) has been proposed, and investigated for implementation on JUICE (Jupiter Icy Moons Explorer)/ RPWI (Radio and Plasma Wave Instrument). When there occurs interference among Jovian radio waves directly from Jupiter (W1), those reflected at the ice crust surface (W2), and those reflected at the subsurface reflectors in the ice crust (W3), fine and wide interference patters can be found in the spectrum. Fine patterns are caused by interference between W1 and W2, and between W1 and W3. Wide patterns are caused by interference between W2 and W3. In order to observe these interference patterns, the receiver of JUICE/RPWI is required to resolve 100 Hz, and possess a downlink spectra with a frequency range of 2 MHz and resolution of 1 kHz. Based on the calculation of the attenuation rate of the radio waves in the ice from 80 K (surface) to 250 K (just above the subsurface ocean), the intensity of the subsurface echo was estimated. The radar waves are expected to reach just above the ice crust/liquid ocean boundary. However, due to extremely high attenuation, it is difficult to detect the echoes from ice crust/liquid ocean boundary. In order to apply the new passive subsurface radar methods, the duration of the coherence of the Jovian radio wave should be long enough (>3.3 ms if spacecraft’s altitude is 500 km).