One of the basic GPS features is its inherent anti-jamming (AJ) characteristics based on great processing gain as a result of using direct sequence spread spectrum (DS-SS) technique. For calculated jamming threshold for GPS receivers operating with L1 C/A, L1 P(Y) and L2 P(Y) signals, jamming range has been analyzed with respect to the characteristic jamming signals and under various effective radiated power of jamming signals. The tests of C/A GPS receiver jamming resistance on different jamming strategies, during the tracking and acquisition phase have been performed. The influence of jamming strategy on jamming efficiency has been proved. At the same time AJ characteristics of GPS receiver have been checked.