The invention discloses a high-load spindle mechanism of a power spinning machine. The high-load spindle mechanism comprises a spindle box provided with an installing hole. The installing hole is internally provided with a spindle, a tapered roller bearing matched with the spindle and a ball bearing; a ring nut which is connected in the installing hole by screw thread is arranged between the tapered roller bearing and the ball bearing; a ring fixing nut arranged at the lower end of the installing hole is connected on the spindle by screw thread; the installing hole is also internally providedwith a seal stress device sleeved on the spindle; the seal stress device, the tapered roller bearing and the wall of the spindle box form a high-pressure oil chamber; and the wall of the spindle box 1 is provided with an oil inlet which is communicated with the high-pressure oil chamber. Through filling the high-pressure oil in the high-pressure oil chamber of the spindle box, a portion of load acting on the spindle is balanced out by the high-pressure oil, so as to reduce the acting force on the spindle box, improve the bearing capacity of the whole mechanism and prolong the service life of the components such as the spindle box, the tapered roller bearing and the like.