Novel polyaspartimides were successfully synthesized via Michael addition reactions involving phosphorus-containing diamines and bismaleimides as monomers and using p-toluenesulfonic acid and N-N-dimethylacetamide as a catalyst and a solvent, respectively. The yields of the polymerization and the molecular weights and inherent viscosities of the polymers increased with the increasing monomers' concentrations, with an upper limit of 0.92 mol/l. All of the obtained polymers were soluble in organic solvents and showed high glass transition temperatures of 227–256 °C, good thermal stability of 360–427 °C, high char yields of 53–64% in nitrogen and 25–46% in air at 700 °C. ; JNL0001576