The invention discloses a planet frame assembly, an engine speed reducer and an aero-engine. The planet frame assembly comprises a planet frame, the planet frame comprises a cavity used for being connected with multiple planet gear shafts and a hollow shaft located on the axis of the cavity and extending axially, a rear supporting structure is arranged at the rear end of the cavity, a transmission structure used for transmitting torque outwards is arranged at the front end of the hollow shaft, an oil guide sleeve matched with the inner hole wall of the hollow shaft to form an annular oil cavity is arranged in an inner hole of the hollow shaft, and at least one oil nozzle is correspondingly arranged at the position, located on the annular oil cavity, of the outer wall of the hollow shaft and is used for lubricating and cooling the gear transmission structure outside the hollow shaft; a radial hole is radially formed in the cavity and used for guiding lubricating oil into the cavity to cool the transmission structure. The transmission reliability of the device is improved, supporting and lubricating structures can ensure safe and effective operation of the engine speed reducer, and the engine speed reducer is particularly suitable for the aero-engine which is large in structural size, high in rotating speed and large in load and transmission ratio.