The invention discloses a main pole of a separately excited DC (Direct Current) motor, comprising a main pole iron core (1), main pole windings (2), slot wedges (3), cushion blocks (4), conformal felts (5) and epoxy air-drying paint (6), wherein two opposite sides of the main pole iron core (1) are coated with the epoxy air-drying paint (6), the outer side of which is pasted with the conformal felt (5) respectively; the main pole iron core (1) coated with the epoxy air-drying paint (6) and pasted with the conformal felts (5) is wound with the main pole windings (2); the cushion blocks (4) andthe conformal felts (5) are respectively arranged between the main pole windings (2) and the main pole iron core (1); the slot wedges (3) are respectively embedded in the main pole iron core (1) andthe cushion blocks (4); and steps are formed between the upper surfaces of the main pole windings (2) and the upper surface of the main pole iron core (1). The invention overcomes many disadvantages of the prior art, realizes slowing of the insulation ageing course of the motor, prolongs service life of the motor and ensures safe and reliable operation of the motor for a long time.