Polyaspartic acid derivative was synthesised with sulfourea ( CSN) and polysuccinimide ( PSI ) that was the thermal condensation polymer of MA. The reaction condition of PSI and CSN was optimized. The product structure was characterized by FT-IR. And the scale inhibition properties and mechanism of CSN-PASP were studied. The result indicates that the scale inhibition efficiency of CSN-PASP is optimum in CSN with 1 . 0 g under the condition of 100 ℃ and 2 . 5 h with CSN to ring opening of PSI. FT-IR proves that amide bond was generated through aminos of sulfourea and carboxyls and the new functional groups are increased on the side chain. CSN-PASP with 10 mg / L, the scale inhibition efficiency is up to 90 % .