Focused on the characteristics of construction industry, referencing the Cobb-Douglas Function, the authors bring forward the theoreticcalculation formula, whichreflects the contribution of IT to construction enterprise production. And based on this,by referencing the NPV function, the authors propose the economy benefitcalculation formulafor calculating the application of IT. These can be used to value the application of IT for contractors, and help the contractors make a strategic decision for enterprise informatization.