In aerospace engineering, it is demanded to design a power system of high-reliability, high performance and strong anti-interference ability, to ensure the life of the spacecraft and its reliable operation. The DC/DC converter has been widely used in the secondary power supply in aerospace engineering attributing to its reliability, high integration, small size, high efficiency. But in the DC conversion process, it is easy to introduce various forms of interference and noise, which directly affects the quality of power supply, and consequently affects the spacecraft's technical performance. To solve the interference problem and improve the reliability of the secondary power supply, a number of key techniques have been discussed on the DC/DC design applications, including: soft-start, filter, Electromagnetic Compatibility (EMC), reliability. After taking corresponding measures, reliability of the secondary power supply has been greatly improved, with surge current being reduced to 1/20 of the original level, and the output ripple being reduced to 1/4 of the original level. The measured data of the CE (Conduction emission) and RE (Radiation emission) tests in the EMC were under the limitation of GJB 151A-97. Results of the experiments and actual application show that the anti-interference design is effective.