The analytical study of the electromagnetic field in a circular waveguide with linearly moving boundary has been made in [1]. In this paper, we analyse the case where the argument of the LEGENDRE's associate functions is superior to 1. The W.K.B. method is used for solving this problem. The expressions of field have been determined. It is shown that the field has a modal nature and the modes are dynamics, each having an instantaneous frequency. Also a criterium of precision is given.