The invention relates to a processing method for a planet carrier. The processing method comprises the following steps that (1), after the planet carrier is subjected to rough processing, a splined hole is formed in a vertical broaching machine in a broaching manner; (2), the planet carrier is inserted into a high-precision-taper spline mandrel, axially and tightly wedging is performed by means ofthe taper, a jacking tip of a numerically controlled lathe tightly jacks center holes in the two ends of the spline mandrel, and a small end face of the planet carrier is subjected to finish turning;(3), the small end face of the planet carrier is placed on a bottom plate, positioning is performed through the splined hole and the small end face, the splined hole serves as the positioning benchmark, three planetary gear mounting holes are formed in a vertical machining centre, and the relative positions of the three planetary gear mounting holes are guaranteed by equipment precision; (4), thesplined hole and the small end face serve as the positioning benchmark, and processing of three blank portions is completed. Positioning is performed through the splined hole, the positioning benchmark is consistent with the design benchmark, the position precision is effectively guaranteed, the main precision is guaranteed by a high-precision fixture and the equipment precision of the machiningcenter, less human factors exist, and quality stability is high.