A simple theoretical model of a Iossless nonideal junction circulator is described. The model consists of a matched lossless n-port junction with a lossless two-port connected to each arm. The basic thought behind it is to separate the reflecting properties of the circulator from the other ones. For the case n=3, unsymmetrical as well as symmetrical junctions are treated. For a symmetrical three-port, the justification of the model has also been experimentally verified. In the case n=4, a symmetrical junction is treated. Flow graphs are used for visualizing the scattering matrices of combined networks and for calculating the coefficients of them.