Effect of some amino phosphonates, in simulated conditions on crystallization rates of calcium oxalate monohydrate crystals (COM) was studied .In the absence of additives , it was found that, the rates of crystallization of prepared COM crystals, were directly proportional to the pH values of medium and inversely proportional to ionic strength of medium. The order of reaction was equal nearly to two and activation energy was 0.144 KJ/mol. In the presence of additives A1,A2,A3,A4 and A5, it was found they were inhibited the rates of crystallization of COM seed crystals through adsorption on the surface of the crystals. Langmuir isotherm can be applied and the calculated KL values in the presence of (A1,A2,A3,A4 and A5) were (12.5 x 10 5 , 11 x 10 5 , 7 x 10 5 , 4.167 x 10 5 , 1.714 x 10 5 ) J/mol respectively indicating strong inhibitory effects of these additives. The values of ΔG in the presence of these additives were ` ( -40.4, -40.0, -39.0,-38.5,-38.2) respectively. Crystallization of prepared COM crystals in presence of 10 -7 mol dm -3 of A1 ,indicated the adsorption of molecules of A1 on both kink and terrace sites , but favored kink sites. The percentage of total surface covered by molecules of A1 additive was 25.6 % which supported the surface-controlled mechanism. These synthesized compounds A1,A2,A3,A4 and A5, were screened for their in vitro antibacterial activity against both Gram positive and Gram negative bacteria. A1 compound showed moderate sensitivity on staph.aureus with slightly activity on klebsiella pneumon.