A novel model was brought in to estimate scaling potential, crystalline form and scaling mass, which has been paid increasingly attention in the industrial due to the significant effect of scale on the normal operation in reverse osmosis (RO) and nanofiltration (NF) systems. Many researches have proved that there exists the interaction between calcium sulfate and calcium carbonate, which is very important to investigate the crystallization process. However, previous models, estimating either calcium sulfate or calcium carbonate, can't estimate the scaling potential of the mixture of the two components. Therefore, it is essential to develop a more cost-effective and efficient model so as to elucidate the effect of the interaction between calcium sulfate and calcium carbonate. Moreover, additional attention should also been paid to the effect of concentration polarization (CP) and pressure which is related to the solubility product constant of calcium carbonate. Based on the above consideration, the scale of calcium sulfate and calcium carbonate was studied in RO and NF systems from the data of publications and ours. The results imply that this model will have potential application to process the data and to estimate scaling potential, crystalline form and scaling mass in RO and NF systems. (C) 2012 Elsevier B.V. All rights reserved.