  Considering the aging effects of existing Inner Drift Chamber (IDC) of
BES\uppercase\expandafter{\romannumeral3}, a GEM based inner tracker is
proposed to be designed and constructed as an upgrade candidate for IDC. This
paper introduces a full simulation package of CGEM-IT with a simplified
digitization model, describes the development of the softwares for cluster
reconstruction and track fitting algorithm based on Kalman filter method for
CGEM-IT. Preliminary results from the reconstruction algorithms are obtained
using a Monte Carlo sample of single muon events in CGEM-IT.
