Shanghai Mass Rapid Line 4 shield tunnels cross the operating Line 2 with 1.03 m distance beneath the operating line 2, small angle and small turning radius. The tunneling-across was carried out without ground improvement. This project took great challenge to the operating line. The influence of the tunnel crossing was predicted and a scientific construction scheme and measures were arranged to guarantee safe operation of Metro Line 2. The construction was performed based on the following principle strictly “to push step by step slowly, to turn equably with short step, to maintain stable pressure, and to improve the foundation with lower pressure and small amount.” Thanks to these measures, the shield tunnel crossed Metro Line 2 successfully.