In this paper, the shield tunneling crosses existing tunnel constructed by mining method without load is presented in detail. The conclusions drawn are as follows: 1)The primary construction quality and late over/short break of primary support and guide platform effect tunnel axial line directly. 2) The quantity and location of backfilling material effect the forcing load of shield advancing directly. The analysis and calculation results show that the actual monitoring value of backfilling material reaches 110%, the synchronous grouting volume reaches 80%, and the stress control lead a predominant effect during supplemental grouting.