Motor internal cooling system and submersible motor

The utility model relates to the technical field of motors, in particular to a cooling system in a motor and a submersible motor, the cooling system comprises a machine barrel, a stator, a rotor, a main shaft, an upper end cover assembly and a lower end cover assembly, and a shielding sleeve is arranged between the stator and the rotor. The inner wall of the shielding sleeve, the outer side surface of the lower part of the main shaft, the outer side surface of the rotor and the outer side surface of the upper part of the main shaft sequentially form a channel I in which a cooling medium can flow; the main shaft is internally provided with a channel II in which a cooling medium can flow, the upper end part of the channel II is communicated with the upper end part of the channel I through a connecting channel, and the lower end part of the channel II is communicated with the lower end part of the channel I through a circulating cavity in the lower end cover assembly; the inner wall of the shielding sleeve is pr