Abstract: The detection range of radar is prominently influenced by evaporation duct. Because the flight .altitude of anti ship missile is lower or a little higher than the height of evaporation duct, in many cases evaporation duct impacts on detection range at detecting antiship missile with surface ship. For this reason, the electromagnetic wave propagation was simulated numerically by parabolic equation and step-Fourier algorithm under the condition of evaporation duct, and the maximum detection range was calculated by assessment mode of radar detection at different atmospheric environments and frequency bands of radar, and different reflected target cross sections and flight altitudes of missile. The simula?tion results show that the performance of S band radar is better than X band，s on most conditions in the presence of evaporation ducts.

Key words: electronics , evaporation duct , radar detecting , antiship missile