The Electron-ion collider in China (EicC) is a proposed future electron-ion collider with a high luminosity above 2.0 × $10^{33}$ $cm^{-2}·s^{-1}$ and center-of-mass energy ranging from 15 to 20 GeV. Excellent particle identification (PID) is essential for the study of exclusive and semi-inclusive processes and 3D imaging of the nucleon structure in the EicC experiment. To meet its PID requirement, a focusing DIRC detector is proposed, which consists of fused silica radiators, optical focus lens, and MCP-PMT photosensor array. In order to study and optimize its performance, we conducted a GEANT4 simulation involving various optical transmission and image reconstruction algorithms. The simulation results demonstrate a high angular resolution of ~ 1mrad, achieving the 3σ Pion/Kaon separation in the momentum up to 6GeV/c.