In this paper, stripline circulator including a ferrite resonator which is consisted of a circular disk and two annuli disks is designed and fabricated. Using RGF(Recursive Green Function) technique, electromagnetic field of port and input impedance is presented. The circulator characteristics are compared according to the ferrite arrangement, bias field intensity and port width. The pass-band frequency of the fabricated circulator using the designed data is from 1.55 GHz to 2.95 GHz, the reflection coefficient $S_{11}$ of input port is -30 dB, and the transmission coefficient $S_{21}$ between input port and isolation port is -28 dB at resonating point 2.38 GHz.