The aim of this study is to certify the performances of a new type high-effective scale inhibitor we have developed for calcium sulfate scale inhibition. The inhibitor is a non-phosphorous copolymer with multi-functional groups, and its; molecular weight is controlled to assure its high efficiency of scale inhibition. Compared with the known scale inhibitors of Flocon-135 and Flocon-100 by means of beaker experiments, it is proved that the performances of the new type inhibitor are of low dose, high tolerance for calcium ions, steady inhibition efficiency at the wide range of pH and iron concentration in the feed water, and little scale in a longer period at a certain dosage of inhibitor.