Abstract: An inorganic scaling is one of the most severe problem in the process of oilfield water injection development. Scale results in lots of economic loss during oil production, especially low permeability oil field, loss too much. So injected water and formation water are carried out to scientific prediction and the reasonable scale prevention measure is put forward for low permeability oil field economic development. In this paper, old prediction methods are compared, inorganic scale saturation index equation founded by virtue of ion association theory and classic solution theory, the Prediction Software of Inorganic Scaling(PIOS1.0)developed. Scale degree of formation water is predicted for several oil fields. Scaling is the most serious near well bore zone and it agrees with scale in situ basically.