The utility model relates to an excavation supporting field specifically is an abundant and the bad dark pit excavation supporting construction of geology of groundwater, and solve current building pit construction and exist and strut that the effect is unsatisfactory, the bulk strength is poor, construction period is long, the high costs scheduling problem, including the precipitation well laid along foundation ditch outside interval suitable for reading, the lasson steel board pole in the excavation supporting stake limit outside in the interval excavation supporting stake and the interval of laying all around along the foundation ditch end opening, be equipped with the I-steel crossbeam between excavation supporting stake and the lasson steel board pole, the locating hole is offered to each excavation supporting stake side, and the spacer bar is established in the locating hole interpolation, and I-steel crossbeam level is set up on the spacer bar, lasson steel board pole and the outside welding of I-steel crossbeam, dark building pit construction's security had both been guaranteed to the combined supporting system that adopts well-points dewatering, lasson steel board pole and excavation supporting stake to form, also guaranteed the time limit for a project, again greatly reduced construction cost, produced good economic benefits and social.