Increasing environmental concerns and discharge limitations have imposed additional challenges in industrial cooling water treatment. Increasing research efforts have been directed towards finding economical and environmentally friendly inhibitors. In this study, a novel inhibitor of low phosphorus co-polymer was prepared. The inhibition performance of the novel low phosphorus co-polymer as calcium sulfate dihydrate scale inhibitors, the influence of phosphorus content and viscosity weighted average molecular weight on inhibition were evaluated in simulated cooling water. The results indicate that the optimal preparation conditions of the novel low phosphorus co-polymer for inhibiting calcium sulfate dihydrate were 2.103 of sodium rho-styrene sulfonate/maleic anhydride ratio, 0.26 of the ratio of hypophosphorous to monomer, and 0.57 of the ratio of hydrogen peroxide to hypophosphorous. The novel low phosphorus copolymer strongly affected the calcium sulfate dihydrate scale formation, the scale inhibition rate was 94%, and phosphorus content and viscosity weighted average molecular weight also evidently influence the scale inhibition rate to calcium sulfate dehydrate. Scanning electronic microscopy and powder X-ray diffraction investigations reveal that the crystal structure of the calcium sulfate dehydrate is highly modified in the presence of the novel low phosphorus co-polymer. (C) 2014 Elsevier B.V. All rights reserved.