Abstract: The rapid cycling synchrotron (RCS) is a main part of the China Spallation Neutron Source (CSNS). The H^- beam from the linac is striped to the proton beam and injected into the RCS, and then the proton beam is accelerated to 1.6 GeV to strike the target. When the beam passes through the wall current monitor (WCM) installed in the RCS, the beam information can be induced in the WCM. The mismatch between RF and the dipoles in the ring can make the beam oscillation deviated from that of the theoretical prediction. The detailed analysis of the WCM was done to get the synchrotron tunes, beam frequencies, the charge density in the bunch and the bunch shape variation, which facilitates the beam commissioning in CSNS/RCS. Meanwhile, the error effects were also analyzed in the process of the parameter measurements.