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 0.92mol/l. All of the obtained polymers were soluble in organic solvents and showed high glass transition temperatures of 227-256 o C, good thermal stability of 360-427 o C, high char yields of 53-64% in nitrogen and 25-46% in air at 700 o C.