The application of CREC shield machines and LOVAT shield machines in the construction of the second phase of No. 6 line and the Exhibit Center branch line of Chongqing rail transit system are studied. The major causes for the abnormal center cutter damage, shield jamming, serious screw conveyor wearing and frequent motor malfunction are analyzed. Key points to which attention should be paid during shield tunneling in fullface hard rock conditions, which include changing the traditional concept, building up new hard rock excavation concept, improving the cutting tool management, rationally selecting boring parameters and strictly controlling the shield position, are proposed. The paper can provide guidance for the improving of the shield tunneling technology.