The invention discloses a cogging method for a large GH4738 high-temperature alloy ingot. According to the method, a bar billet with even and fine grains is obtained through multiple times of heading, drawing, forging and cogging conducted on a homogenized alloy steel ingot, so that the requirement for control over homogeneity of the fine-grained microstructure of the large-size alloy forge piece is met. In the forging and cogging control process, the cogging temperature, deformation amount and deformation speed are strictly controlled, heading, drawing and cogging are conducted repeatedly, forging is conducted by the adoption of glass lubricants and a coating insulation mode, and finally the bar billet of the even fine-grained microstructure is obtained. The cogging method can be applied to cogging and forging of the large GH4738 nickel-based high-temperature alloy ingot to produce the fine-grained bar billet.