In order to reduce the brittleness of polyurea (PUA) aerogel, reactive incorporation of linear long-chain poly-1,4-butanediol bis(4-aminobenzoate) (P1000) into PUA backbone was made by reacting mixed diamines with triisocyanates. The mixed diamines were composed of 4,4 0 -diaminodiphenylmethane (MDA) and P1000. PUA aerogels were produced by freeze-drying. The effect of P1000 percentage and solid content on the properties of PUA aerogel was investigated. It was found that the little addition of P1000 has a reinforcing and toughening effect on PUA aerogels, where the samples maintain a high extent of hydrogen bonding and low linear shrinkage, with a more compact and homogeneous microstructure. The resulting aerogels show apparent density between 0.05 and 0.18 g/cm 3 , surface area between 41 and 179 m 2 /g, and initial decomposition temperature of about 300 C. At 10% solid content and 15 mol % P1000 (in mixed diamines), the overall performance is optimal, with low apparent density (0.113 g/cm 3 ), low thermal conductivity (0.021 W/m K), and high modulus (compressive modulus 7.4 MPa; flexural modulus 18.8 MPa).