The principle and experiment technique of detecting the hostile optical devices based on reflection are described in this paper.Three kinds of detecting method are researched contrastively by the method of ray tracing:①the “Cat′s eye” effect;②the similar “Cat′s eye” effect;③the “surplus reflection” effect.Research results show that the probability of “cat′s eye” reflection is very low in the field environment.But in the right conditions,the probability of the similar “Cat′s eye” effect and the “surplus reflection” effect reflection is much bigger,which is of practical value for the combat field reconnaissance.