In this paper we take helical coordinates, which first appeared in literature [5], and get a series of solution in §3, under the condition of a?b, where a is the radius of cylindrical tube and b that of helical wires. In §4, we discuss the properties of slow wave propagation and point out, upon some limit case, it is similar to general cylindrical wire. In §5, we take part in helical waveguide belonging to fast wave. After some approximation we derive two characteristic equations for the simplest case, but upon them no numerical calculation is carried out. If it is necessary, we may do it later. In general, the paper is featured by a more exact but still more complex calculation.