This paper investigates the key technical problems in designing the construction monitoring system of railway soft soil foundation. The database structure of the monitoring system, which plays an important role in data management, is discussed first. Then the ways to build the platform of data collection, navigation and analysis system are presented, which is based on the treatments of multiple-inheritance of data access document classes. Finally the Realization of software system is reported, and the engineering application in Kunshan experimental site of Beijing-Shanghai high-speed Railroad demonstrates that the monitoring system can improve the efficiency of data process greatly and satisfy the requirements of the large-scaled soft soil subgrade construct with high class railway.