Abstract: From the field components of polarization mode along the horizontal direction in(rectanglar) and curved tunnel,the formula of attenuation rate of transmission of(electromagnetic) wave was deduced under the condition of boundary,thereby the relation curve between attenuation rate of transmission of(electromagnetic) wave and bend radius and the changed curve between attenuation rate of transmission of(electromagnetic) wave and frequency were gotten.The results indicated that the attenuation rate of trans-(mission) of electromagnetic wave would greatly increased if curve exists.Under the condition of bend radius constant,the attenuation rate would increase along with frequency if frequency exceeds over a certain(value.) And its changing range relates with bend radius,the smaller the radius is,the quicker the atten-(uation) rate increases.If curvature radius is small,the higher the frequency is,the larger the attenuation rate is.But when curvature radius is large than a certain value,then the higher the frequency is,the smaller attenuation rate is.