Abstract：On the basis of the multimode loss model in rectangular tunnel,in order to simplify the formula of propagation loss,the formula of roughness loss is deduced using the method of integral which change the discrete form of various modes accumulation to the continuous integral forms of grazing angle. And detailed comparison the two forms of propagation loss formulas and roughness formulas were analyzed. It draws the conclusion that the two forms of loss formula are the same as the change trend of the related factors,the integral representation has simple structure,easy to calculation and simulation analysis. On the basis,uses simulation to further study of the influence of tunnel cross section area,roughness and frequency to reflection loss,roughness loss and propagation loss,draws some useful conclusions.

Keyword：rectangular tunnel;electromagnetic wave propagation loss model;roughness;integral form;