The invention relates to the technical field of petroleum gas well cementation and completion tools, and discloses a well cementing head, which comprises a body tube, an upper joint, a lower joint, a packing rubber plug, a left stop pin shell, a right stop pin shell, stop pin devices and a rubber plug indicating device, wherein both sides of the middle part of the body tube are provided with a left tube hole and a right tube hole respectively; the left stop pin shell and the right stop pin shell are fixedly arranged on the body tube on the outer sides of the left tube hole and the right tube hole respectively; and the stop pin devices which can be opened for moving the packing rubber plug downwards are arranged in the left stop pin shell and the right stop pin shell respectively. The well cementing head has a reasonable and compact structure, and is convenient to use; the left and right stop pin devices can be conveniently and reliably opened through a left rotating rod and a right rotating rod, the descending of the packing rubber plug can be reliably judged through the rubber plug indicating device, and well cementation accidents are effectively avoided; and the well cementing head has the characteristics of simple structure, safety, reliability, low cost, convenience for maintaining and reusability.