Planing-forming is a new process to machine fin heat sinks. This paper investigates the effects of the tool rake angle on the curved radius during planing-forming process by 2-D coupled thermo-mechanical finite element method and experiment verification. With the increasing of the tool rake angle from 0° to 30°, the curved radius increased. When the tool rake increased form 30°to 60°, the curved radius turned stable. After the chip displaced from the tool rake, the fin’s curling up due to the distribution gradient of the residual strain.