To meet the torpedo fiber optic guidance system communication needs and achieve the information exchange between torpedo and ship, a kind of lowloss communication filter was designed and manufactured. The films were prepared by the depositing method of dual ion beam sputtering, through the comparative study of several targets. Based on the requirements of the lowloss filter, a new type of alloy target and SiO2 target were chosen as sputtering materials. In order to broaden the shortwave cutoff region of the filter, the longwave pass film was added behind the initial film, and the thicknesses of the matching layers were optimized, based on the concept of equivalent refractive index. The insertion loss of the passband of the filter was reduced by 0.12 dB. In the preparation of the film, the optical extreme value method and average time method were used to monitor layers′ thickness. By using the method of correct the thickness of irregular layers in proportion, the layers′ thickness control accuracy was improved. The proposed filter basically meets the demand of torpedo fiber optic guidance system through performance test.