[en] An exact mathematic solution of internal and external boundary problem for determination of tensor regular Green functions was found for electric and magnetic vector potential of a round waveguide. It was shown that for a synphase thread-like current source the Green function is described by simple series which in quasi static approximation can be represented by elementary expressions. A relation between the regular Green functions of point and thread-like current sources is established. The obtained results may be applied for design of UHF installations as well as for antenna and accelerating techniques using charged round waveguides. 5 refs. (author)