The underground pipeline network (UPN) is an essential underground structure and infrastructure. Its full-cycle digital twin system is an important part of the smart city. However, traditional information transmission between humans and computers lacks understanding and interaction in the digital twin experiments. From the perspective of perception, a space interaction system based on mixed reality (MR) technology is used to solve the problem of interaction for traditional mechanical experiments. Firstly, during the design phase, Building Information Modeling (BIM) is used to integrate models and information storage, including physical geometry data and material information. Secondly, the analytical algorithm is constructed for sensors by data filtering and material mechanics theory; based on sensors communication, C#/C++, and Socket to develop human–computer interactive methods through Game Engines and Mixed Reality Toolkits (MRTK). Finally, based on comparing the mechanical parameters, the testing of digital pipeline experiments by spatial anchors. Twenty-four experimenters are selected to test this method. The advantages and prospects of spatial interaction with MR are summarized through qualitative and quantitative analysis. This study realizes the data perception of the UPN and maps it to the real environment, which can provide a technical reference for engineering digital experiments.