Abstract: In order to improve the work efficiency,guarantee the quality of design,and provide a base for the safe and economic operation of the power unit,establishment of a mathematical model for the sizing of flash tank is necessary,and it is possible to develop a computer system for sizing the flash tanks by Visual Basic 6.0.ActiveX data objects are made use of by OLE DB Provider to access data in the data servers,and manage the fundamental data.It can attain easy and flexible operation,has high efficiency in the design,and reduce evident errors as well.