In GPS repeater deception jamming, time-delay is a key technique, when time-delay is illogical, receiver's clock off-sets will be changed, deception jamming can be identified easily and the success rate of the deception jamming will be reduced. The theory of GPS Pseudo-range is used in this paper to derive the time-delay algorithm and analyze the effect of different calculation results on receiver's clock off-sets. The conclusion is obtained as that when the distance between transmitted satellite and jammer plus the distance between jammer and the real locus is no more than the distance between transmitted satellite and fictitious locus, jamming has no effect on receiver's clock off-sets, otherwise it has an effect on receiver's clock off-sets. From this point of view, the deployment location of jammer is analyzed: while the jammer is situated on the line formed by satellite and real locus, the selection scope of fictitious locus with no effect on receiver's clock off-sets is the largest.