Abstract: Objective: In response to the unable excavating the soil beneath existing pipelines problem of conventional trenching machines with hydraulic clamshells, a construction technique for diaphragm wall crossing existing pipelines is explored. Method: Taking the construction of the mainbody retaining structure at Xinghuadao Station of Tianjin Metro Line 7 phase I project as research background, the improved structure of conventional trenching machine with hydraulic clamshells is introduced. The construction process after improvement is introduced: trench wall triaxial mixing pile reinforcement, deep guide wall fabrication, assembly of clamshell trenching, segmented production and hoisting of reinforcement cages, as well as the connotation of concrete pouring, specific construction process and key points are explained. Engineering application effects of the improved diaphragm wall construction procedures are compared and analyzed. Result & Conclusion: The proposed construction technique addresses the challenge of unable constructing diaphragm walls when it is very hard to cut and modify the existing pipelines during the retaining structure construction process. Engineering practice shows that compared to the commonly used airlifted reverse circulation suction construction method, this technique effectively reduces construction costs and shortens the construction period. Key wordsmetro; diaphragm wall; trench wall reinforcement; trenching; reinforcement cage