The invention discloses a wellhead sealing device. The wellhead sealing device comprises a shell which can be arranged outside a sucker rod in a sleeving mode, a plurality of sealing rings located ina first sealing space and a second sealing space and elastic pieces arranged on the sealing rings; the shell is provided with the first sealing space and the second sealing space; the first sealing space is located above the second sealing space; the cross-sectional area of one of the first sealing space and the second sealing space is gradually increased from top to bottom, and the cross-sectional area of the other one of the first sealing space and the second sealing space is gradually reduced from top to bottom; the multiple sealing rings are up-down sequentially laminated and arrayed so asto be arranged outside the sucker rod in a sleeving mode, the sealing rings are provided with at least two parts separated from each other in the circumferential direction, a separation gap is formedbetween the at least two parts in the circumferential direction, and the separation gaps of the at least two sealing rings are staggered in the circumferential direction; and the elastic pieces exerts acting force for shrinking the separation gaps in the circumferential direction to the sealing rings. The wellhead sealing device can play a very good sealing role on an oil well wellhead.