The invention discloses an efficiently oil-cooled electric motor comprising a rotating shaft and a rotor core sleeving the rotating shaft. The two axial ends of the rotor core are axially fixed by a rotor end plate. The efficiently oil-cooled electric motor further comprises an oil guiding plate disposed in the axial middle portion of the rotor core. The oil guiding plate is provided therein witha plurality of radial oil guiding plate oil passages. The rotating shaft is provided therein with an axial hollow rotating shaft oil passage. The rotor core is provided therein with an axial rotor core oil passage. The rotor end plate is provided with an end plate groove, at a side close to the rotor core, communicating with the rotor core oil passage. The two ends of each oil guiding plate oil passage communicate with the rotating shaft oil passage and the rotor core oil passage respectively. The rotor core oil passage conveys the cooling oil into the rotor core through the oil guiding platefor cooling. The outer surface of the rotor core is cooled through the end plate groove. The rotor core is cooled when a stator winding is cooled. By using a guide plate, it is avoided that the radialoil passage is directly disposed on the rotor core to destroy the rotor magnetic steel.