Structure noise of marine gearbox seriously affects warship’s concealment, stability of transmission system and amenity of crew working environment. There are many ways to control structural vibration. To add damping in reduction gear box is an effective measurement to suppress box resonance. The key to design damping structure is to determine the parameters of the structure. In most instances, the structural parameters depend on experience and many experiments, which is lengthy and expensive. This paper made an analysis at design stage of reduction gear product by finite element method. This can determine the parameters of box structure, and reduce the input effectively. This method has important theoretical value and application prospect.