The development of techniques for measuring attenuation of a piece of rectangular waveguide is discussed. Measurement is carried out on the basis of the reflection of resonator formed by waveguide.Measurements are performed on waveguide of different lengths

（0.76m

0.60m

0.22 m and 0.09 m） different materials

and different manufacturing methods. Experimental data show that when attenuation of waveguide is on the order of 0.1 db

the random error is about 1.5%

and the total error is more than 10%. With such method it is easy to distinguish waveguide of different materials.Method of selecting parameter of waveguide element for given accuracy is considered. Accuracy is verified by a standard vane type attenuator.