During thermoplastic injection moulding process, the gradual increase of the coolant temperature along the conformal cooling channel (CCC) inside the rapid tool reduces the rate of heat transfer from the polymeric melt to the cooling channel surface at the outlet portion. Injection moulded defects such as irregular warpage of the part between the coolant inlet and outlet cannot be avoided. Rapid tooling (RT) technology offers a speedy and automatic method for rapid tool design and fabrication integrated with complex internal structure such as CCC. This paper presents a novel adjustment method for cooling distance modification between the CCC and its mould cavity (or core) surface along the cooling channel. The proposed method can compensate the gradual increase of the coolant temperature from the coolant inlet to the coolant outlet. More heat can be transferred from the mould surface near the coolant outlet to the proposed variable distance conformal cooling channel (VDCCC). In this study, the cooling channel distance modification relies on two adjustment attributes: (1) the adjustment direction and (2) the adjustment amount, between the mould cavity (or core) surface (terrain) and the cooling channel axis (polyline) after the linearized approximation. A computer-aided melt flow analysis tool of moldflow plastics insight is employed in the case study in order to demonstrate the feasibility of the proposed method. The cooling performance of the proposed VDCCC design can be verified.