© 2016 by NACE International.The formation of scales that is caused by calcium salt in heat exchanger or cooling tower proses is lead to serious problems such as pollution and decreasing of heat transfer. In this study, the effect of crosslinked polymers on the crystallization of calcium oxalate has been investigated in aqueous solutions. Vinylphosphonic acid (VPA) and ethylene glycol methacrylate phosphate (EGMP) with different N,N-Methylene bis acrylamide (MBA) contents have been synthesized for testing as additives for calcium oxalate inhibition. The effect of the polymer on the rate of crystallization of calcium oxalate have been determined by recording the decrease in [Ca2+] as a function of time in a solution. Since additives have great influence on crystal size and shape, we investigated the selective effect of the polymer on the crystal morphology and size using scanning electron microscopy. All the results of the present investigation indicate that VPA inhibit crystal growth due to the fractional coverage of adsorption sites. The inhibition of calcium oxalate crystallization by crosslinked polymers decreased with increasing MBA content. The results show that VPA is a more effective inhibitor than EGMP.