This paper proposes a novel application of topology optimization method for designing replacement of the damaged part for emergency support and rush-repair based on additive manufacturing. The cooling fan of an airplane is investigated as an example. Based on the analysis of the service environment and rush-repair requirement, the replacement part of the damaged cooling fan should be designed for additive manufacturing using alternative to the materials of the original part. Meanwhile, the weight and the moment of inertia of the replacement part should be kept as equal as possible to those of the original part. Accordingly， the topology optimization formulation is established to minimize the overall structural compliance under the interval constraints of the weight and the moment of inertia of the whole structure. Sensitivity analysis is carried out consider the design-dependent effects of the centrifugal forces. According to the topology optimization result and the analysis data of the re-modelled structure, the obtained replacement part meets the requirements of performances and additive manufacturing process. Finally, the replacement part is successfully printed using Selective Laser Melting, demonstrating the proposed method is effective for additive manufacturing.