Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
With GEANT3 frame, we simulate the lead-scintillating fiber type barrel shower counter (BSC) of BES III. The structure of BSC in the simulation is analogous to Phi Factory's, and it's thinkness is 14.4X(o),. The simulations show that the shower time information read-out is necessary for improving the Z spatial resolution the pi (o) invariant mass resolution and for rejecting fake photons. Also, the energy resolution sigma (epsilon)/E (=6 % /rootE), the relation of phi angle resolution sigma (phi) with readout granularity and the relations of mass resolution of pi (o) sigma (m)/m with light yield, attenuation length, readout granularity are given, where m is the invariant mass of pi (o) reconstructed by two photons.