Abstract: The transhorizon signal over the Bohai sea which is realized under the condition of the duct at X band with a length of 107 km is analyzed statistically. The fast fading distribution and the combined fast and slow fading distribution are given in this paper. The theoretical results show that the transhorizon received level in the case of evaporation duct is much higher than the level of troposphere scatter and nearly as same as the case of free space. The experimental results show that the signal amplitude distribution is approximately Rayleigh distribution when it is occurred on July 15 and it is approximately combined lognormal and Rayleigh distribution with a standard deviation of 4~10 dB when it is occurred on July 18. The received signal of July 15 is 40 dB higher than the troposphere scattering signal. The received signal of July 18 is enhanced due to ducting and nearly the extent as the troposphere scatter propagation in the lower.