Located in gravel strata, the fourth bid section of Phase I project of Line 4 of Chengdu Metro is built by an EPB shield. In the paper, the harmonized control of the key boring parameters is analyzed in terms of advance speed, thrust, cutterhead torque, muck releasing quantity, simultaneous grouting and excavation chamber pressure, so as to ensure the stability of the tunnel face and to ensure safe and efficient boring. The causes for the difficulties encountered in tunneling, including rotation of segment rings, boring along smallradius curves and delayed settlement, are analyzed and countermeasures are proposed, so as to ensure good works quality.