Abstract: Ultra-wide band transmission link is widely used, but with the continuous improvement of RF bandwidth, spurious transmission becomes more and more serious, which will cause serious interference to other radio equipment. This paper starts with the mechanism of the stray in ultra-wide band transmission link, analyzes the composition of the stray, and discusses the suppression method for the frequency conversion stray and noise, which have great influence and are difficult to deal with. The effectiveness of the method is verified by experiments, and the stray performance is greatly improved.