A series of potassium alkali salts (K3PO4, K2HPO4, KH2PO4, K2CO3, KHCO3) were applied in CO2 conversion to polyureas. It was observed that the catalytic activity was related to the alkalinity of salts and solvents. K3PO4 was found to be a highly active catalyst for the polymerization of CO2, and various polyureas were achieved from inferior to superior yields. Characterization of spent catalyst by IR and XRD demonstrated that the K3PO4 was completely transformed into less active K2HPO4, KH2PO4 and KHCO3 via reaction with CO2 and water during the polymerization process. The products were examined by IR, 13C NMR, TGA and DSC, indicating that the product obtained from CO2 possesses the ureas structure and good thermal stability.