This thesis discusses about the successful crossings beneath Metro Line1 in operation within short distance by the shield machine in Bid 2 of Guangzhou Metro Urban Distribution System (it is only 2.275m between the top of the excavating face of the shield and Metro Line 1 and during the crossing beneath of the existing lines by shield machine, the shield machine also faces such problem that the cutter head has been pushed into the receiving station while the end of the shield machine still is beneath the existing line during or after the boring of the tunnel). By the investigation and sorting of the structure and status quo of tunnel for Line 1 and multi-review of the plans before crossing of the shield machine, the shield construction is skillfully and dynamically divided into three stages during the construction process and the boring section of the shield machine is prolonged. Automatic information monitoring is decisively introduced to the existing metro lines in advance to direct the construction. Timely follow-up of the decision-making group for emergency and emergency measures, advance maintenance of shield machine, technology of timely cutter replacement and adoption of pre-grouting, grouting with steel pipe and prolonging of the tunnel are the safeguards that make the crossing beneath the existing lines within short distance succeed.